Ionic, electrical, and secretory effects of inhibitors of arachidonic acid metabolism in mouse pancreatic beta-cells.

Abstract

Mouse islets were used to study the effects of inhibitors of cyclooxygenase and lipoxygenase pathways on insulin release, ionic fluxes, and beta-cell membrane potential. The cyclooxygenase inhibitors, Na-salicylate and Na-acetylsalicylate, potentiated glucose-induced insulin release, despite a decrease in Ca influx evidenced by inhibition of the Ca-dependent electrical activity in beta-cells and 45Ca efflux from islets perifused with a medium containing Ca. This paradox can probably be explained by a mobilization of intracellular Ca (acceleration of 45Ca efflux in the absence of Ca) with subsequent activation of K+ channels (acceleration of 86Rb efflux) and repolarization of the membrane. These effects of salicylate could not be ascribed to a change in intracellular pH because they were not mimicked by 2-Cl-benzoate, which has a similar pK as salicylate but increased insulin release by stimulating Ca influx in beta-cells. Among the other cyclooxygenase inhibitors tested, indomethacin caused a slight potentiation of insulin release accompanied by marginal increases in 45Ca efflux and electrical activity, whereas flurbiprofen and ibuprofen were ineffective. Among the lipoxygenase inhibitors, compound BW 755c reversibly decreased glucose-induced insulin release by inhibiting Ca influx in beta-cells, but nordihydroguaiaretic acid had no effect. Inhibitors of arachidonic acid metabolism have effects on ionic fluxes and beta-cell membrane potential, which may explain some of the changes in insulin release they produce.