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Journal of Pharmacology And Experimental Therapeutics Fast Forward
First published on October 7, 2003; DOI: 10.1124/jpet.103.058248


0022-3565/04/3081-47-53$20.00
JPET 308:47-53, 2004
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GASTROINTESTINAL, HEPATIC, PULMONARY, AND RENAL

Signal Transduction Underlying Carbachol-Induced Contraction of Rat Urinary Bladder. I. Phospholipases and Ca2+ Sources

Tim Schneider, Peter Hein, and Martin C. Michel

Departments of Medicine (T.S., P.H., M.C.M.) and Urology (T.S.), University of Essen, Essen, Germany; and Department of Pharmacology and Pharmacotherapy, University of Amsterdam, Amsterdam, The Netherlands (M.C.M.)

Received August 6, 2003; accepted September 24, 2003.


    Abstract
 Top
 Abstract
 Materials and Methods
 Results
 Discussion
 References
 
We have reexamined the muscarinic receptor subtype mediating carbachol-induced contraction of rat urinary bladder and investigated the role of phospholipase (PL)C, D, and A2 and of intra- and extracellular Ca2+ sources in this effect. Based on the nonsubtype-selective tolterodine, the highly M2 receptor-selective (R)-4-{2-[3-(4-methoxy-benzoylamino)-benzyl]-piperidin-1-ylmethyl}-piperidine-1-carboxylic acid amide (Ro-320-6206), and the highly M3 receptor-selective darifenacin and 3-(1-carbamoyl-1,1-diphenylmethyl)-1-(4-methoxyphenylethyl)pyrrolidine (APP), contraction occurs via M3 receptors. Carbachol stimulated inositol phosphate formation in rat bladder slices, and this was abolished by the phospholipase C inhibitor 1-(6-[([17{beta}]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-1H-pyrrole-2,5-dione (U 73,122; 10 µM). Nevertheless, U 73,122 (1–10 µM) did not significantly affect carbachol-stimulated bladder contraction. Carbachol had only little effect on PLD activity in bladder slices, but the PLD inhibitor butan-1-ol, relative to its negative control butan-2-ol (0.3% each), caused detectable inhibition of carbachol-induced bladder contraction. The cytosolic PLA2 inhibitor arachidonyltrifluoromethyl ketone weakly inhibited carbachol-induced contraction at a concentration of 300 µM, but the cyclooxygenase inhibitor indomethacin (1–10 µM) remained without effect. The Ca2+ entry blocker nifedipine (10–100 nM) almost completely inhibited carbachol-induced bladder contraction. In contrast, 1-[{beta}-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole HCl (SKF 96,365; 10 µM), an inhibitor of store-operated Ca2+ channels, caused little inhibition. We conclude that carbachol-induced contraction of rat bladder largely depends on Ca2+ entry through nifedipine-sensitive channels and, perhaps, PLD, PLA2, and store-operated Ca2+ channels, whereas cyclooxygenase and, surprisingly, also PLC are not involved to a relevant extent.


Muscarinic acetylcholine receptors are the physiologically most important mechanisms to elicit contraction of the urinary bladder (Andersson, 1993Go). In the bladder of various mammalian species, including humans, M2 and M3 muscarinic receptors coexist, but the expression of M2 receptors is much greater than that of the M3 receptors (Wang et al., 1995Go; Goepel et al., 1998Go; Yamanishi et al., 2000Go; Kories et al., 2003Go). Nevertheless, the contractile response to the exogenous agonist carbachol and to endogenous agonists released by field stimulation have been attributed predominantly, if not exclusively, to M3 receptors in rats (Longhurst et al., 1995Go; Hegde et al., 1997Go; Tong et al., 1997Go; Braverman et al., 1998Go; Choppin et al., 1998Go; Longhurst and Levendusky, 2000Go; Kories et al., 2003Go), mice (Choppin and Eglen, 2001bGo), pigs (Yamanishi et al., 2000Go), dogs (Choppin and Eglen, 2001aGo), and humans (Chess-Williams et al., 2001Go; Fetscher et al., 2002Go). Moreover, at least male M3 (but not M2) receptor-knockout mice exhibit bladder distension and develop urinary retention (Matsui et al., 2000Go). On the other hand, it should be considered that hitherto available antagonists have only modest subtype selectivity and/or do not act in a purely competitive manner; hence, they were not well suited for detecting a potential minor component of M2 receptors in bladder contraction. The present study was primarily designed to determine the proximal signaling mechanisms underlying M3 receptor-mediated contraction of rat urinary bladder, but we have also reinvestigated the role of muscarinic receptor subtypes using two novel and highly M2- and M3-selective antagonists, i.e., (R)-4-{2-[3-(4-methoxy-benzoylamino)-benzyl]piperidin-1-ylmethyl}-piperidine-1-carboxylic acid amide (Ro-320-6206) (Zhao et al., 2001Go) and [3-(1-carbamoyl-1,1-diphenylmethyl)-1-(4-methoxyphenylethyl)pyrrolidine] APP (MacKenzie and Cross, 1991Go), respectively.

The prototypical signal transduction mechanism of M3 receptors is stimulation of a phospholipase (PL)C to generate inositol phosphates and diacylglycerol (Caulfield and Birdsall, 1998Go). Muscarinic stimulation of PLC has also been demonstrated in cultured smooth muscle cells from human bladder (Marsh et al., 1996Go) and in rat bladder slices (Kories et al., 2003Go), and the latter response was shown to be M3 receptor mediated. However, muscarinic receptors can also activate a PLD or PLA2 in a variety of cell types (Felder, 1995Go), the latter possibly leading to cyclooxygenase activation (Nishimura et al., 1995Go). Several cyclooxygenase products can contract isolated detrusor muscle (Andersson, 2000Go), and cyclooxygenase activation was shown to at least partly mediate rat urinary bladder contraction induced by protease-activated receptor-2 (Nakahara et al., 2003Go). Therefore, we have determined the possible roles of PLC, PLD, PLA2, and cyclooxygenase in muscarinic M3 receptor-mediated contraction of rat urinary bladder.

Similar to all other types of smooth muscle, urinary bladder contraction evoked by muscarinic receptor stimulation involves elevations of intracellular Ca2+ concentrations in rat and guinea pig bladder smooth muscle cells (Ikeda et al., 2002Go; Ma et al., 2002Go). Accordingly, L-type Ca2+ entry blockers can inhibit muscarinic receptor-mediated bladder contraction in guinea pigs and humans (Sjögren et al., 1982Go; Masters et al., 1999Go; Ikeda et al., 2002Go). However, Ca2+ sources apart from L-type channels may also contribute in human bladder smooth muscle cells (Masters et al., 1999Go; Visser and van Mastrigt, 2000Go). Therefore, we have also determined the roles of nifedipine-sensitive and receptor-operated Ca2+ channels in M3 receptor-mediated rat bladder contraction.


    Materials and Methods
 Top
 Abstract
 Materials and Methods
 Results
 Discussion
 References
 
Force of Contraction. Urinary bladder strips were prepared from female Wistar rats (body weight 231 ± 9 g, bladder weight 65 ± 2 mg) obtained from the central animal breeding facility at the University of Essen. Experiments were performed as previously described (Kories et al., 2003Go). Briefly, longitudinal bladder strips (approximately 1 mm diameter, 18 ± 1 mm length, and 9.6 ± 0.5 mg weight, n = 95) were mounted under a tension of 10 mN in 10-ml organ baths containing Krebs-Henseleit solution (119 mM NaCl, 25 mM NaHCO3, 4.7 mM KCl, 1.18 mM KH2PO4, 1.17 mM MgSO4, 2.5 mM CaCl2, 0.027 mM EDTA, 5.5 mM glucose, and 10 mM HEPES), which was aerated with 95% O2 and 5% CO2 to yield a pH of 7.4 at 37°C. After 60 min of equilibration, including washes with fresh buffer every 15 min, the bladder strips were challenged three times with a combination of 50 mM KCl and 0.1 mM carbachol with 5-min rest and washes between each challenge. After washout and an additional 30 min of equilibration, cumulative concentration-response curves were constructed for carbachol in the absence of any inhibitor or vehicle. Using 15-min washouts and then 15-min equilibration periods in between, up to four additional curves were then generated in the presence of increasing concentrations of the indicated antagonists and inhibitors, their negative controls, or their vehicles. Previous work had shown that carbachol-induced rat bladder contraction remains fairly stable under these conditions (Kories et al., 2003Go).

Carbachol concentration-response curves were analyzed by fitting sigmoidal curves to the experimental data, in which the bottom of the curve was fixed at 0. The force of contraction in the absence and presence of inhibitors were expressed as the percentage of maximum carbachol effects observed within the same bladder strip in the first concentration-response curve, i.e., before addition of any inhibitor or vehicle. To assess inhibitor effects, alterations in Emax or pEC50 in its presence relative to the first curve were compared with those in the presence of a matching vehicle time control using two-way analysis of variance testing for main treatment effect and concentration dependence; if this indicated statistical significance, the effect of individual inhibitor concentrations relative to time-matched controls was assessed by Bonferroni post tests. p < 0.05 was considered to be significant in all statistical analyses. To assess antagonist effects, analysis according to Arunlakshana and Schild (1959Go) was performed. All curve fitting and statistical calculations were performed with the Prism program (version 4.0; GraphPad Software Inc., San Diego, CA).

Phospholipase C activation was assessed as [3H]inositol phosphate formation in 350 x 350-µm bladder slices as previously described (Kories et al., 2003Go). Briefly, slices were suspended in 10 ml of Ringer solution (147.2 mM NaCl, 4.0 mM KCl, 2.25 mM CaCl2, 10 mM glucose, and 20 mM HEPES at pH 7.4) supplemented with 10 mM LiCl to block inositol phosphate degradation and 2 U/ml adenosine deaminase. They were incubated for 60 min at 37°C in the presence of 100 µCi of [3H]myoinositol/12 ml. Thereafter, 300 µl of the slice suspension (corresponding to 6–8-mg slice wet weight) were pipetted into flat-bottom polystyrene tubes under gentle swirling, and agonists and antagonists were added in the indicated concentrations to yield a final volume of 330 µl. After incubation for 45 min, the reaction was stopped by addition of 400 µl of ice-cold methanol and 700 µl of chloroform. The mixture was vigorously vortexed twice, and thereafter, the phases were separated by centrifugation at 820g for 10 min at 4°C. Aliquots (450 µl) of the upper phase were placed on Dowex AG1-X8 columns (200 mg per column). Free inositol was eluted twice each with 5 ml of H2O and 5 ml of 60 mM ammonium formate. Total inositol phosphates were eluted twice by addition of 1 ml of 1 M ammonium formate dissolved in 100 mM formic acid. Each data point was measured in quadruplicate within each experiment. Statistical significance of differences was determined by one-way analysis of variance; if this indicated significant differences among group means, individual groups were compared by Dunnett's multiple comparison tests.

Phospholipase D was assessed as [3H]phosphatidylethanol ([3H]PEtOH) formation. The bladder was quickly removed and stored in buffer containing 147.2 mM NaCl, 4 mM KCl, 2.25 mM CaCl2, 20 mM HEPES, and 1 mg/ml glucose at 37°C and a pH of 7.4. Bladder slices of 200 x 200 µm were prepared as described above. The suspension was resuspended and incubated twice with adenosine deaminase (2 U/ml) for 15 min each. Next, the slices were resuspended in 7 ml of fresh buffer containing 40 µl of [3H]oleic acid (specific activity, 5 mCi/ml) and again incubated at 37°C for 60 min. After resuspending the slices in fresh buffer containing 5% (v/v) ethanol, they were incubated in a total volume of 400 µl with the indicated drugs for 45 min at 37°C. Afterward, the incubation was stopped by adding 0.5 ml each of ice-cold methanol, trichloromethane, and H2O. The mixture was vortexed vigorously twice and centrifuged for 10 min at 2000g and 4°C. Four hundred microliters of the lower phase were put into small reaction tubes, and the solvent was evacuated using a SpeedVac centrifuge. The pellet was then resuspended with 25 µl of a 1:1 mixture of chloroform and methanol, and 20 µl were placed on silica gel 60 thin-layer chromatography plates (Whatman, Clifton, NJ). The lipids were separated using the organic phase of a mixture of ethyl acetate/isooctane/acetic acid/water (91: 14:21:70 by volume), migrated with authentic standards, and localized by iodine staining. Areas corresponding to the PEtOH standard were scraped into scintillation vials, as were the areas below containing other labeled phospholipids. The formation of [3H]PEtOH was assessed as the ratio of total labeled phospholipids and is given as the percentage of basal.

Chemicals. Carbachol HCl, nifedipine, SKF 96,365 [1-[{beta}-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole HCl], U 73,122 [1-(6-[([17{beta}]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-1H-pyrrole-2,5-dione], and U 73,343 [1-(6-[-([17{beta}]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-2,5-pyrrolidinedione] were obtained from Sigma-Aldrich Laborchemikalien (Seelze, Germany). AACOCF3 (arachidonyltrifluoromethyl ketone), indomethacin, and phorbol myristyl acetate were from Calbiochem (Bad Soden, Germany). [3H]myoinositol (specific activity, 115 Ci/mmol) was from Amersham Biosciences Inc. (Piscataway, NJ), and [3H]oleic acid (specific activity, 23 Ci/mmol) was from PerkinElmer Life and Analytical Sciences (Boston, MA). Darifenacin and tolterodine were provided by Pfizer (New York, NY), and Ro-320-6206 and APP were synthesized as previously described (MacKenzie and Cross, 1991Go; Zhao et al., 2001Go).

AACOCF3 (at 10 mM), APP (at 10 mM), darifenacin (at 10 mM), tolterodine (at 10 mM), Ro-320-6206 (at 10 mM), U 73,122 (at 3 mM), U 73,343 (at 3 mM), and phorbol myristate acetate (at 1 mM) were dissolved in dimethylsulfoxide. Indomethacin (at 10 mM) and nifedipine (at 1 mM) were dissolved in ethanol. SKF 96,365 was dissolved at 1 mM in distilled water. The experiments involving nifedipine were performed in light-shielded organ baths.


    Results
 Top
 Abstract
 Materials and Methods
 Results
 Discussion
 References
 
Before addition of antagonist or inhibitor, i.e., in the first curve generated within each bladder strip, carbachol concentration-dependently increased force of contraction with a pEC50 of 5.65 ± 0.03 and maximum effects of 35.4 ± 1.4 mN (n = 127 muscle strips). All further contraction data are expressed as percentage of the maximum carbachol effect within the same preparation before addition of any inhibitor.

Antagonist Experiments. Relative to the first curve in the absence of any antagonist, the second to fifth consecutive curve within a preparation exhibited a pEC50 that was -0.06, 0.05, 0.16, and 0.23 log units smaller, respectively; concomitantly, maximum effects were reduced by -2 ± 5%, 8 ± 9%, 18 ± 11%, and 26 ± 13%, respectively (n = 6). These alterations were taken into account when analyzing the effects of the antagonists. Within the tested concentration range, tolterodine, Ro-320-6206, and APP did not affect maximum carbachol responses in a manner that was significantly different from vehicle (data not shown), whereas 10, 30, 100, and 300 nM darifenacin reduced it by 21 ± 5%, 38 ± 9%, 52 ± 11%, and 60 ± 10%, respectively (except for the highest concentration, all p < 0.05 versus vehicle). All four antagonists concentration-dependently right-shifted the carbachol concentration-response curve (Fig. 1). The Schild regression for the nonselective tolterodine (30–1000 nM) had a slope of slightly less than unity (0.80 ± 0.06) and an x-axis intercept (apparent pA2 value) of 8.93 (95% confidence interval, 8.57–9.42). The Schild regression for the M3-selective darifenacin (10–300 nM) had a slope close to unity (1.11 ± 0.15) and an x-axis intercept (apparent pA2 value) of 8.67 (95% confidence interval, 8.20–9.38). The Schild regression for the M3-selective APP (10–300 nM) had a slope close to unity (1.08 ± 0.15) and an x-axis intercept (apparent pA2 value) of 8.73 (95% confidence interval, 8.24–9.49). The M2-selective Ro-320-6206 had only little effect on the carbachol concentration-response curve. Thus, at concentrations of 0.3, 1, 3, and 10 µM, it right-shifted the carbachol concentration-response curve by only 0.14 ± 0.10, 0.25 ± 0.11, 0.42 ± 0.14, and 0.75 ± 0.16 log units, respectively; accordingly, a Schild slope of only 0.40 ± 0.11 was obtained, and the x-axis intercept of this shallow regression line was 6.72 (95% confidence interval, 5.92–8.53).



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Fig. 1. Schild plots for antagonism of carbachol-induced rat bladder contraction. Data are means ± S.E.M. of six experiments each.

 

Role of Phospholipase C. In confirmation of previous findings from our laboratory (Kories et al., 2003Go), 1 mM carbachol enhanced IP formation by approximately 60% over basal (Fig. 2). This concentration of carbachol had been chosen based on our previously published concentration-response curves to obtain a good signal/noise ratio. Although U 73,122 (10 µM) alone had no effect on basal IP formation, it abolished carbachol-stimulated IP formation (Fig. 2).



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Fig. 2. Effect of carbachol (1 mM), U 73,122 (10 µM), and their combination on inositol phosphate accumulation in rat bladder slices. Data are expressed as percentage of accumulation in the absence of either drug (basal) within the same experiment. *, p < 0.05 versus basal in a one-way analysis of variance followed by Dunnett's multiple comparison test.

 

Nevertheless, U 73,122 (1–10 µM) did not significantly alter the potency or maximum effects of carbachol-induced bladder contraction relative to its vehicle (Fig. 3). In light of the unexpectedness of this finding, it was confirmed for 10 µM U 73,122 in a second series of experiments performed by a different investigator; in that series, U 73,122 failed to significantly affect carbachol-induced bladder contraction not only relative to its vehicle but also relative to 10 µM of its negative control, U 73,343 (n = 11–12; data not shown). Moreover, we confirmed the effectiveness of U 73,122 in organ bath experiments by demonstrating that it markedly inhibited {alpha}1-adrenoceptor-induced contraction of rat mesenteric microvessels (Altmann et al., 2003Go).



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Fig. 3. Effects of the phospholipase C inhibitor U 73,122 (1–10 µM) and its vehicle on carbachol-induced contraction of rat bladder (n = 7).

 

Role of Phospholipase D. PLD activity was markedly stimulated by 1 µM of the positive control phorbol myristyl acetate (210 ± 19% over basal, n = 13). In contrast, 1 mM carbachol had only little effect on PLD activity, i.e., enhanced [3H]PEtOH accumulation nonsignificantly by only 13 ± 10% over basal (Fig. 4).



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Fig. 4. Effects of carbachol (1 mM) and atropine (1 µM) on [3H]PEtOH formation in rat bladder slices. Data are expressed as percentage of accumulation in the absence of either drug (basal) within the same experiment.

 

The PLD inhibitor butan-1-ol did not significantly alter carbachol-induced contraction relative to its negative control butan-2-ol when tested at concentrations of 0.03 or 0.1%, but a statistically significant reduction of potency and maximum effects of carbachol was obtained at a butan-1-ol concentration of 0.3% (Fig. 5).



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Fig. 5. Effects of the phospholipase D inhibitor butan-1-ol (0.03–0.3%) and its negative control butan-2-ol on carbachol-induced contraction of rat bladder (n = 8). *, p < 0.05 versus matching time controls in the presence of negative control in a two-way analysis of variance followed by Bonferroni post tests.

 

Role of Phospholipase A2 and Cyclooxygenase. The PLA2 inhibitor AACOCF3 did not significantly alter carbachol-induced contraction relative to its vehicle when tested at concentrations of 30 and 100 µM, whereas a statistically significant reduction of maximum effects of carbachol (but not of its potency) was observed at an inhibitor concentration of 300 µM (Fig. 6). The cyclooxygenase inhibitor indomethacin (1–10 µM) did not significantly alter the potency or maximum effects of carbachol-induced bladder contraction relative to its vehicle (Fig. 7).



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Fig. 6. Effects of the cytosolic phospholipase A2 inhibitor AACOCF3 (30–300 µM) and its vehicle on carbachol-induced contraction of rat bladder (n = 8). *, p < 0.05 versus matching time controls in the presence of vehicle in a two-way analysis of variance followed by Bonferroni post tests.

 


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Fig. 7. Effects of the cyclooxygenase inhibitor indomethacin (1–10 µM) and its vehicle on carbachol-induced contraction of rat bladder (n = 8).

 

Role of Ca2+ Sources. The Ca2+ entry blocker nifedipine (10–100 nM) markedly inhibited carbachol-induced bladder contraction relative to its vehicle, ethanol (Fig. 8). This inhibition was due to reductions of maximum carbachol responses reaching up to 90% at 100 nM, which were not accompanied by statistically significant alterations of the agonist potency for the remaining response.



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Fig. 8. Effects of the Ca2+ channel inhibitor nifedipine (10–100 nM) and its vehicle on carbachol-induced contraction of rat bladder (n = 6). * and ***, p < 0.05 and <0.001, respectively, versus matching time controls in the presence of vehicle in a two-way analysis of variance followed by Bonferroni post tests.

 

SKF 96,365, an inhibitor of receptor-operated Ca2+ channels, did not significantly affect carbachol-induced bladder contractions at concentrations of 1 or 3 µM, whereas a significant reduction of maximum responses (-47%) but not of carbachol potency was seen with 10 µM SKF 96,365 (Fig. 9).



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Fig. 9. Effects of SKF 96,365 (1–10 µM), an inhibitor of receptor-operated Ca2+ channels, and its vehicle on carbachol-induced contraction of rat bladder (n = 6). **, p < 0.01 versus matching time controls in the presence of vehicle in a two-way analysis of variance followed by Bonferroni post tests.

 


    Discussion
 Top
 Abstract
 Materials and Methods
 Results
 Discussion
 References
 
The present study was primarily designed to investigate proximal signaling mechanisms potentially involved in carbachol-induced muscarinic receptor-mediated contraction of rat urinary bladder. Although M2 receptors are more numerous in rat bladder than M3 receptors (Wang et al., 1995Go; Kories et al., 2003Go), numerous studies have proposed that rat bladder contraction is mediated predominantly if not exclusively by the minor population of M3 receptors (Longhurst et al., 1995Go; Hegde et al., 1997Go; Tong et al., 1997Go; Braverman et al., 1998Go; Choppin et al., 1998Go; Longhurst and Levendusky, 2000Go; Kories et al., 2003Go). However, all of these studies were based on antagonists with only moderate subtype selectivity or on darifenacin, which has considerable selectivity for M3 receptors but does not act purely competitively (as confirmed in the present study). Therefore, we reinvestigated the muscarinic receptor subtype mediating rat bladder contraction using APP (MacKenzie and Cross, 1991Go), a compound that, similar to darifenacin, is about 40-fold selective for M3 receptors (Ki, 2.6 versus 111 nM; S. Hegde, personal communication) but does not reduce maximum responses, and Ro-320-6206, an approximately 100-fold M2-selective antagonist APP (5.0 versus 500 nM; Zhao et al., 2001Go); the nonselective tolterodine and the M3-selective darifenacin were studied in comparison. Using more selective and apparently purely competitive tools, our present experiments confirm that carbachol-induced contraction of rat bladder occurs via M3 receptors.

Coimmunoprecipitation studies demonstrate that the M3 receptors in rat bladder couple predominantly to G-proteins of the Gq/11 and, surprisingly, also the Gi1 type (Wang et al., 1995Go). Activation of a PLC is the prototypical signaling response of Gq-coupled receptors in general and of M3 muscarinic receptors in particular (Caulfield and Birdsall, 1998Go). Muscarinic receptor stimulation also activates PLC in cultured smooth muscle cells from human bladder (Marsh et al., 1996Go) and in rat bladder slices (Kories et al., 2003Go), and at least the latter response is mediated by M3 receptors, i.e., the same subtype mediating the contraction. Studies in feline isolated bladder smooth muscle cells using neomycin as the PLC inhibitor have proposed that PLC activation is important for carbachol-induced bladder contraction (An et al., 2002Go). The present data based on rat bladder strips and U 73,122 as the PLC inhibitor surprisingly do not support this proposal. Although we do not know whether these discrepancies are due to differences in species (rat versus cat), type of preparation (strip versus cultured cell), or PLC inhibitor (U 73,122 versus neomycin), it should be noted that the present study did not detect inhibition of contraction under conditions where PLC activation was clearly abolished within the same study. Thus, at least in rats, M3 receptor-mediated PLC activation and contraction occur concomitantly, but contraction is not dependent on PLC activation.

Activation of PLD is another potential signaling mechanism of M3 muscarinic receptors (Zhou et al., 1994Go; Schmidt et al., 1995Go). In the present study, the PLD inhibitor butan-1-ol, relative to its negative control butan-2-ol, caused some inhibition of carbachol-induced bladder contraction, but the effect was weak and reached statistical significance only at the highest inhibitor concentration. However, butan-1-ol concentrations up to 0.5% can still be considered to be selectively inhibiting PLD (Banno et al., 2001Go; Bechoua and Daniel, 2001Go), and hence, the inhibition by 0.3% butan-1-ol in our study is unlikely to be nonspecific. The small extent of the inhibition is not surprising, since carbachol caused only little if any PLD activation in rat bladder slices, i.e., an effect of less than 10% of the positive control phorbol myristate acetate. Thus, PLD activation appears to play only a minor role in M3 receptor-mediated rat bladder contraction.

Activation of a cytosolic PLA2, possibly followed by that of a cyclooxygenase, is another potential signaling mechanism of muscarinic receptors (Hunt et al., 1994Go; Felder, 1995Go; Nishimura et al., 1995Go). This could potentially also be involved in muscarinic receptor-mediated bladder contraction, since several cyclooxygenase products are known to contract the bladder (Andersson, 2000Go), and since it has recently been shown that rat bladder contraction elicited by protease-activated receptor-2 involves activation of a cyclooxygenase (Kubota et al., 2003Go; Nakahara et al., 2003Go). In the present study, AACOCF3, an inhibitor of cytosolic PLA2, caused only minor, if any, inhibition of rat bladder contraction. Moreover, the cyclooxygenase inhibitor indomethacin, when applied in concentrations inhibiting protease-activated receptor-2-mediated rat bladder contraction (Nakahara et al., 2003Go), was completely ineffective. Thus, cytosolic PLA2 and cyclooxygenase do not appear to play a role for M3 receptor-mediated rat bladder contraction.

Elevations of intracellular Ca2+ concentrations play a central role in smooth muscle contraction. Muscarinic receptor-induced Ca2+ elevations have been demonstrated in rat and guinea pig bladder smooth muscle cells (Ikeda et al., 2002Go; Ma et al., 2002Go). They could come from intracellular stores, e.g., inositol phosphate or ryanodine receptor-sensitive stores, or from the extracellular space via a variety of ion channels. In light of our negative data regarding an involvement of PLC, we have not further investigated a possible role of inositol phosphate-sensitive Ca2+ stores. A role for ryanodine-sensitive Ca2+ stores has previously been demonstrated in muscarinic receptor-stimulated contraction of human detrusor isolated smooth muscle cells (Visser and van Mastrigt, 2000Go). In guinea pig and human bladder smooth muscle cells, L-type Ca2+ channels also appear to contribute to the muscarinic receptor-mediated bladder contractions (Sjögren et al., 1982Go; Masters et al., 1999Go; Visser and van Mastrigt, 2000Go; Ikeda et al., 2002Go). In the present study, the L-type Ca2+ channel inhibitor nifedipine potently and effectively inhibited carbachol-induced bladder contraction. Indeed, this response was much more sensitive to nifedipine- than noradrenaline- or sphingosylphosphorylcholine-induced blood vessel contraction (Chen et al., 1996Go; Bischoff et al., 2001Go). Moreover, knockout mice lacking the Cav1.2 gene, which encodes for a subunit of voltage-operated Ca2+ channels, exhibit a markedly reduced bladder contraction in response to muscarinic stimulation (Wegener et al., 2003Go). In contrast, SKF 96,365, an inhibitor of receptor-operated Ca2+ channels, caused only minor, if any, inhibition of carbachol-induced bladder contraction in the present study. Thus, influx of extracellular Ca2+ through L-type voltage-dependent channels but not through receptor-operated channels appears to play a pivotal role for rat bladder contraction.

In conclusion, carbachol-induced, M3 muscarinic receptor-mediated contraction of rat bladder is largely mediated by Ca2+ influx through L-type, voltage-dependent channels. Surprisingly, PLC activation is not involved, although it is concomitantly activated. Moreover, PLD, PLA2, cyclooxygenase, and receptor-operated Ca2+ channels also play only a minor, if any, role in muscarinic receptor-mediated contraction of rat bladder. The role of various protein kinases, which may be activated secondary to these proximal signaling mechanisms, was determined in the accompanying paper (Fleichman et al., 2004Go).


    Acknowledgements
 
We thank Charlotte Fetscher for skillful technical assistance and Dr. Martina Schmidt for help in setting up the PLD assay.


    Footnotes
 
This work was supported in part by grants from the Deutsche Forschungsgemeinschaft (Mi 294/7-1) and Theravance Inc. T.S. was recipient of a training fellowship from the intramural grant program of the University of Essen Medical School (IFORES).

DOI: 10.1124/jpet.103.058248.

ABBREVIATIONS: Ro-320-6206, (R)-4-{2-[3-(4-methoxy-benzoylamino)-benzyl]-piperidin-1-ylmethyl}-piperidine-1-carboxylic acid amide; APP, 3-(1-carbamoyl-1,1-diphenylmethyl)-1-(4-methoxyphenylethyl)pyrrolidine; PL, phospholipase; PEtOH, phosphatidylethanol; SKF 96,365, 1-[{beta}-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole HCl; U 73,122, 1-(6-[([17{beta}]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-1H-pyrrole-2,5-dione; U 73,343, 1-(6-[-([17{beta}]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-2,5-pyrrolidinedione; AACOCF3, arachidonyltrifluoromethyl ketone; IP, inositol phosphate.

Address correspondence to: Professor Martin C. Michel, Academisch Medisch Centrum, Afd. Farmacologie en Farmacotherapie, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands. E-mail: m.c.michel{at}amc.uva.nl


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Altmann C, Steenpass V, Czyborra P, Hein P, and Michel MC (2003) Comparison of signalling mechanisms involved in rat mesenteric microvessel contraction by noradrenaline and sphingosylphosphorylcholine. Br J Pharmacol 138: 261-271.[CrossRef][Medline]

An JY, Yun HS, Lee YP, Yang SJ, Shim JO, Jeong JH, Shin CY, Kim JH, Kim DS, and Sohn UD (2002) The intracellular pathway of the acetylcholine-induced contraction in cat detrusor muscle cells. Br J Pharmacol 137: 1001-1010.[CrossRef][Medline]

Andersson K-E (1993) Pharmacology of lower urinary tract smooth muscles and penile erectile tissues. Pharmacol Rev 45: 253-308.[Medline]

Andersson K-E (2000) Treatment of overactive bladder: other drug mechanisms. Urology 55 (Suppl 5A): 51-57.[Medline]

Arunlakshana O and Schild HO (1959) Some quantitative uses of drug antagonists. Br J Pharmacol 14: 48-58.[Medline]

Banno Y, Takuwa Y, Akao Y, Okamoto H, Osawa Y, Naganawa T, Nakashima S, Suh PG, and Nozawa Y (2001) Involvement of phospholipase D in sphingosine 1-phosphate-induced activation of phosphatidylinositol 3-kinase and Akt in Chinese hamster ovary cells overexpressing EDG3. J Biol Chem 276: 35622.[Abstract/Free Full Text]

Bechoua S and Daniel LW (2001) Phospholipase D is required in the signaling pathway leading to p38 MAPK activation in neutrophil-like HL-60 cells, stimulated by N-formyl-methionyl-leucyl-phenylalanine. J Biol Chem 276: 31752.[Abstract/Free Full Text]

Bischoff A, Finger J, and Michel MC (2001) Nifedipine inhibits sphingosine-1-phosphate-induced renovascular contraction in vitro and in vivo. Naunyn-Schmiedeberg's Arch Pharmacol 364: 179-182.[CrossRef][Medline]

Braverman AS, Luthin GR, and Ruggieri MR (1998) M2 muscarinic receptor contributes to contraction of the denervated rat urinary bladder. Am J Physiol 275: R1654-R1660.

Caulfield MP and Birdsall NJM (1998) International Union of Pharmacology. XVII. Classification of muscarinic acetylcholine receptors. Pharmacol Rev 50: 279-290.[Abstract/Free Full Text]

Chen H, Fetscher C, Schäfers RF, Wambach G, Philipp T, and Michel MC (1996) Effects of noradrenaline and neuropeptide Y on rat mesenteric microvessel contraction. Naunyn-Schmiedeberg's Arch Pharmacol 353: 314-323.[CrossRef][Medline]

Chess-Williams R, Chapple CR, Yamanishi T, Yasuda K, and Sellers DJ (2001) The minor population of M3-receptors mediate contraction of human detrusor muscle in vitro. J Auton Pharmacol 21: 243-248.[CrossRef][Medline]

Choppin A and Eglen RM (2001a) Pharmacological characterization of muscarinic receptors in dog isolated ciliary and urinary bladder smooth muscle. Br J Pharmacol 132: 835-842.[CrossRef][Medline]

Choppin A and Eglen RM (2001b) Pharmacological characterization of muscarinic receptors in mouse isolated urinary bladder smooth muscle. Br J Pharmacol 133: 1035-1040.[CrossRef][Medline]

Choppin A, Eglen RM, and Hegde SS (1998) Pharmacological characterization of muscarinic receptors in rabbit isolated iris sphincter muscle and urinary bladder smooth muscle. Br J Pharmacol 124: 883-888.[CrossRef][Medline]

Felder CC (1995) Muscarinic acetylcholine receptors: signal transduction through multiple effectors. FASEB J 9: 619-625.[Abstract]

Fetscher C, Fleichman M, Schmidt M, Krege S, and Michel MC (2002) M3 muscarinic receptors mediate contraction of human urinary bladder. Br J Pharmacol 136: 641-643.[CrossRef][Medline]

Fleichman M, Schneider T, Fetscher C, and Michel MC (2004) Signal transduction underlying carbachol-induced contraction of rat urinary bladder. II. Protein kinases. J Pharmacol Exp Ther 308: 54-58.[Abstract/Free Full Text]

Goepel M, Gronewald A, Krege S, and Michel MC (1998) Muscarinic receptor subtypes in porcine detrusor: comparison with humans and regulation by bladder augmentation. Urol Res 26: 149-154.[CrossRef][Medline]

Hegde SS, Choppin A, Bonhaus D, Briaud S, Loeb M, Moy TM, Loury D, and Eglen RM (1997) Functional role of M2 and M3 muscarinic receptors in the urinary bladder of rats in vitro and in vivo. Br J Pharmacol 120: 1409-1417.[CrossRef][Medline]

Hunt TW, Carroll RC, and Peralta EG (1994) Heterotrimeric G proteins containing G{alpha}i3 regulate multiple effector enzymes in the same cell. Activation of phospholipases C and A2 and inhibition of adenylyl cyclase. J Biol Chem 269: 29565-29570.[Abstract/Free Full Text]

Ikeda K, Kobayashi S, Suzuki M, Miyata K, Takeuchi M, Yamada T, and Honda K (2002) M3 receptor antagonism by the novel antimuscarinic agent solifenacin in the urinary bladder and salivary gland. Naunyn-Schmiedeberg's Arch Pharmacol 366: 97-103.[CrossRef][Medline]

Kories C, Czyborra C, Fetscher C, Schneider T, Krege S, and Michel MC (2003) Gender comparison of muscarinic receptor expression and function in rat and human urinary bladder: differential regulation of M2 and M3? Naunyn-Schmiedeberg's Arch Pharmacol 367: 524-531.[CrossRef][Medline]

Kubota Y, Nakahara T, Mitani A, Maruko T, Saito M, Sakamoto K, and Ishii K (2003) Possible involvement of Ca2+-independent phospholipase A2 in protease-activated receptor-2-mediated contraction of rat urinary bladder. Naunyn-Schmiedeberg's Arch Pharmacol 367: 588-591.[CrossRef][Medline]

Longhurst PA, Leggett RE, and Briscoe JAK (1995) Characterization of the functional muscarinic receptors in the rat urinary bladder. Br J Pharmacol 116: 2279-2285.[Medline]

Longhurst PA and Levendusky M (2000) Influence of gender and the oestrous cycle on in vitro contractile responses of the rat urinary bladder to cholinergic stimulation. Br J Pharmacol 131: 177-184.[CrossRef][Medline]

Ma FH, Higashira-Hoshi H, and Itoh Y (2002) Functional muscarinic M2 and M3 receptors and {beta}-adrenoceptor in cultured rat bladder smooth muscle. Life Sci 70: 1159-1172.[CrossRef][Medline]

MacKenzie AR and Cross PE (1991) Pfizer Ltd., UK and Pfizer Inc., assignees. Preparation of 3-(1-carbamoyl-1,1-diphenylmethyl)-1-(phenalkyl)pyrrolidines as muscarinic antagonists. WO 1990-EP2043 (WO 9109013). 1991 Jun 27.

Marsh KA, Harriss DR, and Hill SJ (1996) Desensitization of muscarinic receptor-coupled inositol phospholipid hydrolysis in human detrusor cultured smooth muscle cells. J Urol 155: 1439-1443.[CrossRef][Medline]

Masters JG, Neal DE, and Gillespie JI (1999) The contribution of intracellular Ca2+ release to contraction in human bladder smooth muscle. Br J Pharmacol 127: 996-1002.[CrossRef][Medline]

Matsui M, Motomura D, Karasawa H, Fujikawa T, Jiang J, Komiya Y, Takahashi S, and Taketo MM (2000) Multiple functional defects in peripheral autonomic organs in mice lacking muscarinic acetylcholine receptor gene for the M3 subtype. Proc Natl Acad Sci USA 97: 9579-9584.[Abstract/Free Full Text]

Nakahara T, Kubota Y, Mitani A, Maruko T, Sakamoto K, and Ishii K (2003) Protease-activated receptor-2-mediated contraction in the rat urinary bladder: the role of urinary bladder mucosa. Naunyn-Schmiedeberg's Arch Pharmacol 367: 211-213.[CrossRef][Medline]

Nishimura Y, Usui H, Kurahashi K, and Suzuki A (1995) Endothelium-dependent contraction induced by acetylcholine in isolated rat renal arteries. Eur J Pharmacol 275: 217-221.[CrossRef][Medline]

Schmidt M, Fasselt B, Rümenapp U, Bienek C, Wieland T, van Koppen CJ, and Jakobs KH (1995) Rapid and persistent desensitization of M3 muscarinic acetylcholine receptor-stimulated phospholipase D. Concomitant sensitization of phospholipase C. J Biol Chem 270: 19949-19956.[Abstract/Free Full Text]

Sjögren C, Andersson K-E, Husted S, Mattiasson A, and Moller-Madsen B (1982) Atropine resistance of transmurally stimulated isolated human bladder muscle. J Urol 128: 1368-1371.[Medline]

Tong Y-C, Hung Y-C, Lin S-N, and Cheng J-T (1997) Pharmacological characterization of the muscarinic receptor subtypes responsible for the contractile response in the rat urinary bladder. J Auton Pharmacol 17: 21-25.[CrossRef][Medline]

Visser AJ and van Mastrigt R (2000) The role of intracellular and extracellular calcium in mechanical and intracellular electrical activity of human urinary bladder smooth muscle. Urol Res 28: 260-268.[CrossRef][Medline]

Wang P, Luthin GR, and Ruggieri MR (1995) Muscarinic acetylcholine receptor subtypes mediating urinary bladder contractility and coupling to GTP binding proteins. J Pharmacol Exp Ther 273: 959-966.[Abstract/Free Full Text]

Wegener JW, Specht V, Lee T-S, Koller A, Feil S, Feil R, Kleppisch T, Klugbauer N, Moosmang S, and Hofmann F (2003) Involvement of L-type calcium channels (CAV1.2) in the carbachol-induced contraction of murine urinary bladder. Naunyn-Schmiedeberg's Arch Pharmacol 367 (Suppl 1): R61.

Yamanishi T, Chapple CR, Yasuda K, and Chess-Williams R (2000) The role of M2-muscarinic receptors in mediating contraction of the pig urinary bladder in vitro. Br J Pharmacol 131: 1482-1488.[CrossRef][Medline]

Zhao S-H, Berger J, Miller AK, Flippin LA, Clark RD, Maag H, Stepan G, Watson N, Shetty SG, Cefalu JS, et al. (2001) Novel 2-benzyl-piperidine derivatives as selective M2 muscarinic receptor antagonists (Abstract), in American Chemical Society Proceedings; 2001 August 26–30; Chicago, IL. 221, ORGN-597.

Zhou X-M, Curran P, Baumgold J, and Fishman PH (1994) Modulation of adenylylcyclase by protein kinase C in human neurotumor SK-N-MC cells: evidence that the {alpha} isozyme mediates both potentiation and desensitization. J Neurochem 63: 1361-1370.[Medline]


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