Rapidly induced modulation of beta-N-acetylglucosaminidase activity in pancreatic islets.

The aim of this work was to determine the possible rapid modulatory effect of glucose on the activity of pancreatic islet lysosomal enzymes. For this purpose, beta-N-acetylglucosaminidase and beta-galactosidase activities were measured in homogenates of isolated rat islets after a 5, 15, 30 or 60-min exposure to either 3.3 or 16.

Identification of the calmodulin-regulated protein phosphatase, calcineurin, in rat pancreatic islets.

The aim of this work was the identification of the calmodulin-stimulated protein phosphatase, calcineurin, in rat pancreatic islets. For this purpose, a high-affinity calcineurin antibody and the Western blotting technique were used to detect the presence of calcineurin in freshly collagenase-isolated islets. The calcineurin content detected by this method was about 0.

Changes in insulin secretion and calcium distribution within B cells induced by gliclazide.

Using the pyroantimonate technique, the ultracytochemical distribution of calcium within B cells was studied in isolated rat pancreatic islets incubated during 5, 15 and 30 min with 8.3 mM glucose alone or together with 76 microgram glicazide. Glucose alone produced a continuous increment in the total number of calcium pyroantimonate precipitates (CPP) throughout the incubation period studied.

Thyroid hormone binding and deiodination by pancreatic islets: relationship with the in vitro effect upon insulin secretion.

Thyroxine dehalogenation by rat pancreatic islets was studied incubating isolated islets with labelled T4. [125I]T4 added to the incubation medium was deiodinated by the islets with the consequent production of T3, rT3 and iodide. This deiodination process showed a clear glucose-dependence, being significantly increased in the presence of 16.

Islet cells-tight junctions: changes in its number induced by glucose.

Cell-tight junctions were counted in rat isolated islets incubated for different periods of time in the presence of different extracellular glucose concentrations. The number of tight junctions increased as a function of the length of the incubation period and the concentration of glucose. These results would suggest the involvement of tight junctions in the regulatory process of glucose-induced insulin secretion.