Basal pancreatic exocrine functions as well as responses to endogenous (BPJ diversion) and exogenous (injection of CCK-8 or secretin) stimulations were examined in young (6- and 12-month-old) and old (24- to 26-month old) female Fischer 344 rats. Basal secretions were not significantly different between young and old rats. BPJ diversion significantly stimulated pancreatic secretions of fluid, bicarbonate, and protein in all animals. The pancreatic protein response (mg/kg/hr) to BPJ diversion was significantly attenuated with respect to age [57.59 +/- 16.16, 43.73 +/- 6.94, and 20.75 +/- 3.95, for 6-, 12-, 24- to 26-month-old rats, respectively, mean +/- SE, F(2,20) = 3.49, P less than 0.05]. The pancreatic responses to secretin (0.086, 0.432, and 1.728 nmol/kg) were not significantly different between young and old rats. Intravenous injection of CCK-8 (0.033, 0.167, and 0.667 nmol/kg) produced a significant increase in protein output in all age groups. In young animals, stepwise increases in protein output were observed, whereas, in old rats, increments in response to the larger two doses of CCK-8 (0.167 and 0.667 nmol) were smaller than that produced by 0.033 nmol/kg of CCK-8. In conclusion, the basal secretions in old rats were comparable with those in young ones, but the reserve capacity for protein secretion appears to decrease in old compared to young rats.