Role of arachidonic acid in hyposmotic membrane stretch-induced increase in calcium-activated potassium currents in gastric myocytes1

Abstract

Aim: To study effects of arachidonic acid (AA) and its metabolites on the hyposmotic membrane stretch-induced increase in calcium-activated potassium currents (I KCa ) in gastric myocytes. Methods: Membrane currents were recorded by using a conventional whole cell patch-clamp technique in gastric myocytes isolated with collagenase. Results: Hyposmotic membrane stretch and AA increased both I K(Ca) and spontaneous transient outward currents significantly. Exogenous AA could potentiate the hyposmotic membrane stretch-induced increase in I K(Ca) . The hyposmotic membrane stretch-induced increase in I K(Ca) was significantly suppressed by dimethyleicosadienoic acid (100 µmol/L in pipette solution), an inhibitor of phospholipase A 2 . Nordihydroguaiaretic acid, a lipoxygenase inhibitor, significantly suppressed AA and hyposmotic membrane stretch-induced increases in I K(Ca) . External calcium-free or gadolinium chloride, a blocker of stretch-activated channels, blocked the AA-induced increase in I K(Ca) significantly, but it was not blocked by nicardipine, an L-type calcium channel blocker. Ryanodine, a calcium-induced calcium release agonist, completely blocked the AA-induced increase in I K(Ca) ; however, heparin, a potent inhibitor of inositol triphosphate receptor, did not block the AA-induced increase in I K(Ca) . Conclusion: Hyposmotic membrane stretch may activate phospholipase A 2 , which hydrolyzes membrane phospholipids to ultimately produce AA; AA as a second messenger mediates Ca 2+ influx, which triggers Ca 2+ -induced Ca 2+ release and elicits activation of I K(Ca) in gastric antral circular myocytes of the guinea pig.

Transient receptor potential canonical type 3 channels facilitate endothelium-derived hyperpolarization-mediated resistance artery vasodilator activity

“…39 Similar reports of a functional interaction of IP 3 R and large-conductance K Ca have also been suggested in isolated basilar artery smooth muscle cells, 40 and in cultured murine pancreatic b-cells, 41 while IP 3 R and IK Ca have been reported to functionally interact in isolated guinea pig gastric smooth muscle cells. 42 Thus, the precedent for functional interaction of TRPC3, IP 3 R, and K Ca exists, supporting the potential spatialrelated functional activity of these channels and receptors in myoendothelial signalling in rat mesenteric arteries. The present data show that in the mesenteric artery of adult male rats, TRPC3 is expressed in endothelial cells.…”

Altered expression of calcium‐activated K and Cl channels in detrusor overactivity of rats with partial bladder outlet obstruction

“…Exposure to hypo‐osmolar solution has been used for generating membrane tension in the cell. This tension can be transferred to the cytoskeleton, which will excite the stretch‐activated channels, similarly to the effect of mechanical stretch load in vivo [31]. Ca 2+ influx and Ca 2+ release were found in detrusor cells in hypo‐osmolar solution [14].…”

Actions and Mechanisms of Polyunsaturated Fatty Acids on Voltage-Gated Ion Channels

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