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

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Abstract:

Abstract Aim:

To study effects of arachidonic acid (AA) and its metabolites on the hyposmotic membrane stretch-induced increase in calcium-activated potassium currents (IKCa) 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 IK(Ca) and spontaneous transient outward currents significantly. Exogenous AA could potentiate the hyposmotic membrane stretch-induced increase in IK(Ca). The hyposmotic membrane stretch-induced increase in IK(Ca) was significantly suppressed by dimethyleicosadienoic acid (100 umol/L in pipette solution), an inhibitor of phospholipase A2. Nordihydroguaiaretic acid, a lipoxygenase inhibitor, significantly suppressed AA and hyposmotic membrane stretch-induced increases inIK(Ca). External calcium-free or gadolinium chloride, a blocker of stretch-activated channels, blocked the AA-induced increase in IK(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 inIK(Ca); however, heparin, a potent inhibitor of inositol triphosphate receptor, did not block the AA-induced increase in IK(Ca). Conclusion:

Hyposmotic membrane stretch may activate phospholipase A2, which hydrolyzes membrane phospholipids to ultimately produce AA; AA as a second messenger mediates Ca2+ influx, which triggers Ca2+-induced Ca2+ release and elicits activation ofIK(Ca) in gastric antral circular myocytes of the guinea pig.

Keywords: arachidonic acid; calcium-activated potassium current; gastric myocyte; hyposmotic membrane stretch

Document Type: Research Article

DOI: http://dx.doi.org/10.1111/j.1745-7254.2005.00201.x

Affiliations: 1: Department of Physiology, Shanghai Jiaotong University School of Medicine, Shanghai 200030; 2: Department of Physiology, Yanbian University College of Medicine, Yanji 133000; 3: East China Normal University School of Life Science, Shanghai 200062, China

Publication date: October 1, 2005

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