This project is designed to evaluate the relationship between phosphatidylinositol metabolism and the secretion of insulin from the stimulated rat pancreatic islet. The substrate and ionic requirements for this phenomenon will be evaluated. The subcellular localization of phosphatidylinositol and its pattern of response to stimulation will be studied by radioautography. Insulin granules will be isolated from stimulated and unstimulated islets by isoelectric focusing and characterized with regard to their surface charge by micro-electrophoresis. The incorporation of arachidonic acid into phosphatidylinositol and its subsequent conversion to prostaglandins will be evaluated. The characteristics and subcellular localization of the enzymes concerned with phosphatidylinositol synthesis and breakdown will be studied in rat nerve and islet. Finally, the mechanisms responsible for the dependence of cultured islets upon exogenous myo-inositol will be evaluated.