Persisting enhanced proinsulin-insulin and protein biosynthesis (3H-leucine incorporation) by pancreatic islets of the rat after glucose exposure.

Pancreatic islets isolated from rats infused with glucose for twenty-four hours incorporated 3H-leucine into protein at higher rates than islets isolated from normoglycemic rats. Incorporation into proinsulin-insulin showed a thirteenfold increase. The effect on other islet proteins was fourfold. Exposure of islets from normoglycemic rats to high glucose in vitro for twenty and ninety minutes and subsequent incubation with 3H-leucine at low glucose showed a twofold and fivefold increase in proinsulin biosynthesis. In the in vitro system pre-exposure of the islets to mannose and dibutyryl-cyclic AMP induced a much smaller increase in proinsulin biosyntheses.