Immunohistological demonstration of insulin in islets of langerhans after stimulation of insulin secretion by glucose, sulphonylureas and insulin antibodies.

Abstract

The immunohistological detection of insulin in whole pancreatic tissue and isolated islets was studied, using cryostat sections, freeze-dried material and in formalin-fixed tissue. Cryotomy produces unsatisfactory results and can only be used as a screening procedure. The freeze-drying technique followed by paraffin embedding is time consuming, but possesses an advantage in that it best guards the natural morphological relationships in cells and tissue. — The results of experiments designed to determine the immunohistologically-provable content of insulin in the islets of Langerhans of rats by means of various stimulants to insulin secretion are reported. Intravenously injected glucose in high concentration (10 g/kg) does not lead to an immunohistologicallyprovable decrease in the insulin content of the beta cells, after either 2, 4 or 24 h. During the first 6 h following a single intravenous medication of tolbutamide (500 mg/kg) or of glibenclamide (1 mg/kg) there is no decrease in the immunofluorescence of the beta cells. The decrease, apparent after 8 h, becomes more clear in a wide range of cells after 12 h, and has reached its climax after 24 h. At this time, nearly all of the cells of the islet are degranulated except those in the periphery. On the contrary, 5 h following intravenous injection of insulin antibodies, an almost total decrease in immunohistologically-provable insulin can be observed.