Calcium antagonists and calmodulin: Effect of verapamil, nifedipine and diltiazem

doi:10.1016/0014-2999(83)90219-4

European Journal of Pharmacology

Volume 90, Issue 1, 20 May 1983, Pages 103-108

https://doi.org/10.1016/0014-2999(83)90219-4 Get rights and content

Abstract

The effect of three calcium antagonists (verapamil, nifedipine and diltiazem) on the calcium-induced activation of phosphodiesterase (a calmodulin dependent process) was investigated. Therapeutically relevant concentrations of verapamil, nifedipine and diltiazem were used. In the presence of calmodulin, phosphodiesterase activity was stimulated by calcium in the range 4 × 10⁻⁶−2.5 × 10⁻⁵ M. Dialtiazem (10⁻⁶ M), verapamil (10⁻⁶ M) and nifedipine (10⁻⁷ and 10⁻⁶ M) had no influence on phosphodiesterase activity in the presence or absence of calmodulin at any concentration of calcium employed. By contrast trifluoroperazine abolished the Ca²⁺ activation of the phosphodiesterase enzyme. From this it is concluded that while the interaction of calcium antagonists with calmodulin may be of interest in the study of the mode of action of calmodulin, it probably does not contribute to their vasodilator activity.

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Interaction of the dihydropyridine calcium antagonist, CD-349, with calmodulin
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The characteristics of the binding of the 1,4-dihydropyridine Ca²⁺ antagonist, 2-nitratopropyl 3-nitratopropyl 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine 3,5-dicarboxylate (CD-349), to calmodulin (CaM) and the effect of CD-349 on the Ca²⁺/CaM-dependent enzyme, cyclic GMP (cGMP) phosphodiesterase (PDE), were investigated. CD-349 showed a Ca²⁺-dependent binding to CaM, in equilibrium column binding studies. CD-349 inhibited the [³H]CD-349 binding to CaM, at a concentration producing a 50% inhibition (ic₅₀) of 2.4 μM, whereas the CaM antagonist, trifluoperazine hydrochloride (TFP), stimulated the [³H]CD-349 binding to CaM. Scatchard plot analysis of the binding of CD-349 to CaM revealed that the apparent dissociation constant (K_app) of CD-349 was 2.1 μM and the maximal number of binding sites (B_max) of CD-349 was 1.0 nmol/nmol CaM. In the presence of TFP, the K_app and B_max values of CD-349 binding to CaM were changed to 1.1 μM and 1.5 nmol/nmol CaM respectively. Although the CaM antagonists, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7) and TFP, decreased and increased, respectively, the fluorescence intensity caused by 2-p-toluidinylnaphthalene -6-sulfonic acid (TNS)-CaM binding, CD-349 only slightly decreased the fluorescence of TNS bound CaM. CD-349 inhibited both basal and Ca²⁺/CaM-activated cGMP PDE activity. However, CaM did not competitively antagonize the CD-349-induced inhibition of the Ca²⁺/CaM-activated PDE activity. In addition, the kinetic study showed that CD-349 inhibited both basal and Ca²⁺/CaM-activated cGMP PDE activity, competitively with cGMP, with almost the same inhibition constant (K_i). These results suggest that CD-349 binds to CaM, with Ca²⁺ dependency, at sites differing from those which bind to the CaM antagonist. The inhibitory activity of CD-349 on Ca²⁺/CaM-dependent PDE does not seem to be due to a CaM antagonistic action.
Effects of dihydropyridine calcium antagonists on rabbit renal Na,K-ATPase activity in vitro
1988, European Journal of Pharmacology
Dihydropyridines are reported to have a stimulatory effect on vascular smooth muscle Na, K-ATPase activity in vitro. We studied the effects of the dihydropyridine calcium antagonists nimodipine, nitrendipine, nitoldipine, niludipine, nifedipine and felodipine (10⁻⁵ M) on purified Na,K-ATPase isolated from rabbit kidney outer medulla. We were unable to detect an effect of the drugs on the enzyme activity, either under optimal or suboptimal substrate conditions. Likewise, NaK-ATPase activity, partly inhibited by the addition of ouabain (10⁻⁶ M), Ca²⁺ (10⁻³ M) or arachidonic acid (4×10⁻⁵ M), was not influenced by the dihydropyridines. The absence of a stimulatory effect of dihydropyridines on renal Na,K-ATPase is in agreement with the known diuretic and natriuretic effects of the drugs in normotensive and hypertensive men.
Calcium Channel Blocking Drugs
1987, Progress in Medicinal Chemistry
This chapter discusses calcium channel blocking drugs. Many new drugs have been developed for the treatment of cardiovascular disorders. One of the most important discoveries has been the existence of drugs that inhibit the entry of calcium ions into cells by blocking the voltage-dependent calcium channels. Because drugs may inhibit the availability of calcium by blocking voltage-dependent calcium channels, by stimulating the efflux of calcium from the cell or by stimulating the uptake of calcium into storage sites, the term calcium antagonist is clearly a rather imprecise one in describing the mechanism of action of such drugs. The use of other terms, such as calcium entry blocker, calcium inhibitor, or slow channel blocking drug, is similarly inexact. Drugs that act through the inhibition of the inward slow calcium current by preventing the passage of Ca²⁺ ions through the calcium channel in the cell membrane are best described as calcium channel blocking drugs. These calcium channel blocking drugs form a diverse group of substances.
Slow calcium channel blockers and calmodulin. Effect of felodipine, nifedipine, prenylamine and bepridil on cardiac sarcolemmal calcium pumping atpase
1985, Biochemical Pharmacology
The effect of four slow Ca²⁺ channel blockers (felodipine, nifedipine, prenylamine and bepridil) that possess the ability to bind to calmodulin (CaM) and to inhibit myosin light chain kinase (MLCK) on CaM-regulated Ca²⁺ pumping ATPase of cardiac sarcolemma (SL) and brain cyclic AMP phosphodiesterase (PDE) was studied. The ability of these drugs to inhibit Ca²⁺ pumping ATPase correlated with their inhibitory effect on CaM-activated Ca²⁺-dependent PDE. Nifedipine was unable to inhibit markedly both enzymes. Prenylamine also was a weak inhibitor, which was unexpected because of its CaM binding potency. Felodipine (10–50 μM) and bepridil (50 μM) markedly reduced activities of SL Ca²⁺ pumping ATPase and PDE. Striking differences were, however, demonstrated when Ca²⁺ and CaM concentrations, respectively, were increased. Previously it was reported that inhibition of the SL Ca²⁺ pumping ATPase by the CaM antagonist calmidazolium could be overcome by increasing Ca²⁺ concentrations (J. M. J. Lamers and J. T. Stinis, Cell Calcium 4, 281–294, 1983). Felodipine (10–50 μM) in the present study, appeared to be equipotent with calmidazolium in reducing Ca²⁺ pumping ATPase, but increasing Ca²⁺ up to 12.2 μM could not counteract this effect. Felodipine (2–10 μM) also inhibited brain PDE noncompetitively with respect to CaM contrary to the competitive effectors calmidazolium and bepridil. On the other hand, bepridil (10–20 μM) decreased or increased Ca²⁺ pumping ATPase activity depending on the Ca²⁺ concentration (0.29 and 12.2 μM, respectively) used. These findings suggest at least two types of CaM antagonists, which can be discriminated on basis of their inhibition patterns of PDE and heart SL Ca²⁺ pumping ATPase.
Effect of depolarizing concentrations of potassium on calcium uptake and metabolism in rat liver
1985, FEBS Letters
Exposure of perfused livers of fed rats to 60 mM K⁺ induces rapid responses in the Ca²⁺-sensitive metabolic events, glycogenolysis, cytoplasmic and mitochondrial NADH/NAD ratios and octanoate oxidation. All increase within 45 s of K⁺ addition. Metabolic responses were not observed following K⁺ addition to livers perfused in the absence of added Ca²⁺. Movements of Ca²⁺ into the liver were suggested from experiments in which ⁴⁵Ca²⁺ uptake was measured. The Ca²⁺ antagonists verapamil, diltiazem and Ni²⁺ essentially abolished changes to tissue metabolism and Ca²⁺ fluxes induced by K⁺ addition. K⁺-induced changes were consistent with Ca²⁺ channel activiation.
LiverPotassium depolarizationGlycogenolysisCalcium antagonist
Effects of felodipine, nitrendipine and W-7 on arterial myosin phosphorylation, actin-myosin interactions and contraction
1984, European Journal of Pharmacology
The relative effects of felodipine, a dihydropyridine with purported calmodulin antagonistic properties, have been compared with the calmodulin inhibitor, W-7, for inhibition of Ca²⁺-dependent force development and direct inhibition of Ca²⁺-calmodulin mediated arterial myosin light chain phosphorylation and actin-myosin interactions. Felodipine (IC₅₀ 3 × 10⁻⁹ M) was approximately 30 000 × more potent than W-7 (IC₅₀ 10⁻⁴ M) and equipotent with another dihydropyridine, nitrendipine, in inhibiting isometric force development in K⁺-depolarized aortic smooth muscle strips. In contrast, W-7 (IC₅₀ 4 × 10⁻⁵ M) was approximately 5 × more potent than felodipine (IC₅₀ 2 × 10⁻⁴ M) in inhibiting Ca²⁺-dependent myosin light chain phosphorylation or superprecipitation of arterial actomyosin. Concentration-related inhibition of both parameters by W-7 was tightly coupled to concomitant inhibition of force development in intact smooth muscle. In contrast, inhibition of myosin light chain phosphorylation and superprecipitation by felodipine was only apparent at concentrations ⩾ 10⁻⁵ M while maximal inhibition of force development occurred at a concentration as low as 10⁻⁷ M. Inhibition of contractility by W-7 was minimal in paced rabbit atria, whereas inhibition by felodipine was similar to that seen with nitrendipine. These results suggest that the pharmacologically-relevant mechanism of Ca²⁺ antagonism in smooth muscle by felodipine is similar to nitrendipine (blockade of the Ca²⁺ entry channel) and does not involve direct inhibition of Ca²⁺-calmodulin stimulated myosin light chain phosphorylation and subsequent actin-myosin interactions.

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Calcium antagonists and calmodulin: Effect of verapamil, nifedipine and diltiazem

Abstract

Biochim. Biophys. Acta

Am. J. Cardiol.

Am. J. Cardiol.

J. Biol. Chem.

Biochem. Pharmacol.

J. Biol. Chem.

Chest

Plasma concentration-response relationship of verapamil in the treatment of angina pectoris

J. Cardiovasc. Pharmacol.

Interaction of the antihypertensive drug felodipine with calmodulin

Nature

Calmodulin plays a pivotal role in cellular regulation

Science