Aim: To investigate the effects of exogenous unsaturated fatty acids on calcium-activated potassium current (I(K(Ca))) in gastric antral circular myocytes of guinea pigs.
Methods: Gastric myocytes were isolated by collagenase from the antral circular layer of guinea pig stomach. The whole-cell patch clamp technique was used to record I(K(Ca)) in the isolated single smooth muscle cells with or without different concentrations of arachidonic acid (AA), linoleic acid (LA), and oleic acid (OA).
Results: AA at concentrations of 2,5 and 10 micromol/L markedly increased I(K(ca)) in a dose-dependent manner. LA at concentrations of 5, 10 and 20 micromol/L also enhanced I(K(Ca)) in a dose-dependent manner. The increasing potency of AA, LA, and oleic acid (OA) on I(K(Ca)) at the same concentration (10 micromol/L) was in the order of AA>LA>OA. AA (10 micromol/L)-induced increase of I(K(ca)) was not blocked by H-7 (10 micromol/L), an inhibitor of protein kinase C (PKC), or indomethacin (10 micromol/L), an inhibitor of the cyclooxygenase pathway, and 17-octadecynoic acid (10 micromol/L), an inhibitor of the cytochrome P450 pathway, but weakened by nordihydroguaiaretic acid (10 micromol/L), an inhibitor of the lipoxygenase pathway.
Conclusion: Unsaturated fatty acids markedly increase I(K(ca)), and the enhancing potencies are related to the number of double bonds in the fatty acid chain. The lipoxygenase pathway of unsaturated fatty acid metabolism is involved in the unsaturated fatty acid-induced increase of I(K(ca)) in gastric antral circular myocytes of guinea pigs.