Pancreatic insulin, glucagon and somatostatin concentrations in rats with islet cell tumors induced by streptozotocin.

Hyperinsulinemic and hypoglycemic rats with islet tumors induced by streptozotocin were shown to have significantly decreased immunoreactive insulin and somatostatin concentration (expressed as per g wet weight (w. wt) and content (expressed as per whole pancreas) in the pancreas surrounding the tumor as compared to those of age and weight adjusted controls. The pancreatic glucagon concentration of the former was significantly lower than that of the latter but no significant difference between glucagon content in the two groups was observed. Thus, inverse relationships were demonstrated between circulating insulin and somatostatin as well as insulin in the pancreas. It is suggested that a large amount of insulin in plasma results in a decrease in pancreatic insulin and somatostatin.