On the mechanism of insulinotropic action of hepoxylins: Evidence of a direct, glucose-independent effect of hepoxylins B3 on insulin secretion

Abstract

The effects of lipoxygenase metabolites of arachidonic acid, hepoxylin B 3 epimers, on insulin secretion by a culture of isolated islet cells were studied. The effect was assessed at hepoxylin B 3 concentrations of 0.2 to 5.0 ~tM and different glucose concentrations in the culture medium. Both hepoxylin B 3 epimers were shown to boost the stimulating effect of glucose on insulin secretion. This effect manifests itself at glucose concentrations of 5.5 and 11 mM and disappears at an above normal glucose content in the medium (20 mM). The capacity of hepoxylin B 3 to stimulate the secretion of insulin by a culture of islet cells in a glucose-free medium has also been demonstrated. This direct, not glucose-mediated, insulinotropic effect may serve as proof that the hepoxylins belong to the category of intracellular messengers.