Control of insulin secretion in the Egyptian sand rat ( Psammomys obesus).

Eighteen sand rats ( Psammomys obesus) maintained on a vegetable or mixed vegetable and laboratory chow diet were bled and their pancreases removed and incubated in vitro to study insulin release. Plasma glucose and insulin measurements showed that all the animals were either normal or had a mild non-ketotic diabetes mellitus-like syndrome. Pancreatic insulin content was high (13 to 20 U/g) and insulin release in basal medium was 5 to 25 times that occurring with pancreas pieces from common laboratory animals. Basal in vitro insulin release correlated with the plasma insulin value at the time of sacrifice. Glucose, tolbutamide and dibutyryl cyclic AMP did not significantly stimulate nor did dopamine inhibit insulin release from pancreases from normal or mildly diabetic sand rats. Glucagon, however, did significantly stimulate in vitro insulin release. Insulin secretion in the sand rat has unique control mechanisms. [ABSTRACT FROM AUTHOR]