Glucose-induced translocation of protein kinase C in rat pancreatic islets

The role of protein kinase C (PKC) as a mediator of glucose-induced insulin secretion has been a subject of controversy. Glucose-induced translocation of PKC has not been reported, and the relevant PKC isoenzymes in islets have not been identified. To address these issues, we developed specific antibodies to the α, β, and γ isoenzymes of PKC. Western blots of homogenates of freshly isolated rat islets probed with these antibodies revealed that the major isoenzyme present is α-PKC. Islets were perifused for 15 min with either 2.75 mM glucose, 20 mM glucose, 20 mM glucose plus 30 mM mannoptulose, 15 mM α-ketoisocaproate, or α-ketoisocaproate plus mannoheptulose. Quantitative immunoblotting of membrane and cytosol fractions showed that α-PKC translocated from the cytosol to the membrane in freshly isolated rat islets stimulated with either 20 mM glucose or 15 mM α-keisiocaproate. Both the secretory response and the translocation of α-PKC were blocked by the addition of mannoheptulose an inhibitor of glucose metabolism, in islets stimulated with glucose but not in islets stimulated with α-ketoisocaproate. These results support a role for α-PKC in mediating glucose-induced insulin secretion in pancreatic islets. (.