The Effect of Dexamethasone on B cell Mass and Function in Partial Pancreatctomized Rats

We have now examined islet mass and B-cell secretory function 19 days following a 40–50% pancreatectomy (Px). Plasma glucose and insulin values in Px were equal to those of sham-operated control rats both in the fed state and following an in traperitoneal glucose tolerance test. Glucose potentiation of arginine-induced insulin secretion remained fully preserved when assessed with the invitro perfused pancreas. On the other hand, 5 days of dexamethasone caused mild hyperglycemia in Px, but not in the control group. Moreover, in vitro insulin secretion from the dexamethasone-treated Px rats tended to be modestly lower than the dexamethasone-treated controls. Islet mass returned to a value not significantly lower than that of shams, with a further 30% increase noted in both dexamethasone-treated groups. In contrast, pancreatic insulin content in both Px groups was only about 40% of comparable controls. These data show almost complete islet regeneration within 3 weeks of the 40–50% pancreatectomy. Islet function, on the other hands, was characterized by limited reserve capacity which coexisted with and may have contributed to the development of mild hyperglycemia in the presence of dexamethasone-induced insulin resistance.