Alteration of insulin and glucagon secretion from the perfused BB rat pancreas before and after the onset of diabetes.

Secretion of insulin and glucagon from perfused BB rat pancreas was examined in rats (5 weeks old; n = 6) before and 2 weeks after (13 weeks old; n = 5) the onset of diabetes mellitus. The secretion of insulin and glucagon was modified by increasing concentrations of glucose in the perfusate from 2.8 mM to 16.5 mM. In 5-week-old BB rats, glucagon secretion was higher at the low glucose concentration (2.8 mM) and insulin secretion lower at the high glucose concentration (16.5 mM) than the corresponding values in age-matched control rats. In 13-week-old BB rats, insulin secretion was undetectable irrespective of glucose concentration. Glucagon secretion was only moderately suppressed by the perfusion of high glucose (16.5 mM) and was significantly higher than that of age-matched controls. The reduction in insulin secretion observed in 5-week-old rats without insulitis indicated that pancreatic B cells of BB rats of this age are somehow injured by humoral factors rather than cell infiltration. Cell function was apparently modified indirectly by the destruction of neighboring B cells.