ARACHIDONIC-ACID INDUCES PHOSPHORYLATION OF AN 18 KDA PROTEIN IN ELECTRICALLY PERMEABILIZED RAT ISLETS OF LANGERHANS

Arachidonic acid (AA) was shown to induce concentration-dependent, calcium-independent, in situ phosphorylation of a protein of approximate molecular weight 18 kDa in electrically permeabilised rat islets of Langerhans. This protein did not appear to be a substrate for protein kinase C (PKC) since stimulation of PKC by 4-beta phorbol myristate acetate (4-beta PMA) did not result in P-32 incorporation into an 18 kDa protein, and since AA-induced phosphorylation was observed in islets in which PKC had been down-regulated by prolonged exposure of islets to 4-beta PMA. These results suggest that AA stimulates protein phosphorylation by a mechanism other than PKC activation.