Abstract
Arachidonic acid metabolites such as prostaglandins, thromboxanes, and leukotrienes are well known modulators of intestinal vascular perfusion, motility, and electrogenic ion transport. We investigated the effect of different hydroxyeicosatetraenoic acids (HETEs) from cytochrome P450- and lipoxygenase-dependent arachidonate metabolism on electrogenic chloride secretion in rat distal colon. Using conventional Ussing techniques, basolateral 12-HETE significantly decreased basal short-circuit current (Isc) and inhibited furosemide-sensitive Cl− secretion stimulated by either dibutyryl cAMP, prostaglandin E2, or theophylline in a concentration-dependent manner (IC50 = 1.5 nM). These data were underlined by significant inhibition of JnetCl in unidirectional 36Cl flux measurements. Direct regulation of the basolateral Na+-K+-2Cl− cotransporter or the Na-K-ATPase could be excluded because 12-HETE had no effect on furosemide-sensitive K+ secretion induced by epinephrine, or ouabain-sensitive Na+ reabsorption stimulated by aldosterone. Inhibitors of Ca2+-activated and voltage-gated K+ channels such as apamin, charybdotoxin, and dendrotoxin did not affect secretagogue-dependent Isc and its regulation by 12-HETE. In contrast, glibenclamide significantly attenuated the effect of 12-HETE on secretagogue-induced Isc, whereas chromanol 293B, an inhibitor of cAMP-dependent K+ conductance, had an additive effect. We speculate that 12-HETE, like glibenclamide, affects intestinal Cl−secretion by inhibiting basolateral K+ATPchannels. In contrast to these findings, neither 5-HETE nor 20-HETE had any effect on basal Isc or cAMP-dependent Cl−secretion.
Footnotes
-
Send reprint requests to: Dr. Markus Wegmann, Department of Pediatrics, Philipps University Marburg, Deutschhausstr. 12, D-35037 Marburg, Germany. E-mail:wegmannm{at}mailer.uni-marburg.de
-
↵1 This study was supported by grants from Deutsche Forschungsgemeinschaft (Ko 1642/1-1) and Stiftung P.E. Kempkes, Marburg (Kz. 26/93).
- Abbreviations:
- AA
- arachidonic acid
- CYP450
- cytochrome P450
- HETE
- hydroxyeicosatetraenoic acid
- VTE
- transepithelial voltage
- ΔVTE
- voltage deflections
- RTE
- total tissue resistance
- Isc
- short-circuit current
- DBcAMP
- dibutyryl cAMP
- PGE2
- prostaglandin E2
- ‰
- per thousand
- JnetCl
- net chloride flux
- mTAL
- medullary thick ascending limb
- Received April 7, 2000.
- Accepted June 30, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|