Immunocytochemical localization of α-protein kinase C in rat pancreatic β-cells during glucose-induced insulin secretion

Abstract

To investigate the role of protein kinase C (PKC) in the regulation of insulin secretion, we visualized changes in the intracellular localization of α-PKC in fixed β-cells from both isolated rat pancreatic islets and the pancreas of awake unstressed rats during glucose-induced insulin secretion. Isolated, perifused rat islets were fixed in 4% paraformaldehyde, detergent permeabilized, and labeled with a mAb specific for α-PKC. The labeling was visualized by confocal immunofluorescent microscopy. In isolated rat pancreatic islets perifused with 2.75 mM glucose, α-PKC immunostaining was primarily cytoplasmic in distribution throughout the β-Cells. In islets stimulated with 20 mM glucose, there was a significant redistribution of α-PKC to the cell periphery. This glucose-induced redistribution was abolished when either mannoheptulose, an inhibitor of glucose metabolism, or nitrendipine, an inhibitor of calcium influx, were added to the perifusate. We also examined changes in the intracellular distribution of α-PKC in the β-cells of awake, unstressed rats that were given an intravenous infusion of glucose. Immunocytochemical analysis of pancreatic sections from these rats demonstrated a glucose-induced translocation of α-PKC to the cell periphery of the β-cells. These results demonstrate that the metabolism of glucose can induce the redistri-bution of α-PKC to the cell periphery of β-cells, both in isolated islets and in the intact animal, and suggest that α-PKC plays a role in mediating glucose-induced insulin secretion.