INCIDENCE OF APOPTOSIS IN THE PANCREAS OF YOUNG AND OLD RATS

We reported previously that the pancreatic protein responses to the hi gh dose of cholecystokinin (CCK) or bile-pancreatic juice diversion we re impaired in old rats of both sexes, whereas the basal secretion was comparable to that in young animals. To examine the mechanism of the attenuated response in old rats, we examined the incidence of apoptosi s of the pancreatic acinar cells and the plasma CCK concentrations pro duced by bile-pancreatic juice diversion, which is a potent endogenous stimulator of pancreatic secretion, in young (4-8 months old) and old (25-29 months old) rats of both sexes. Apoptosis was examined by elec tron microscopic examination and the nick end-labeling method for dete cting cells with DNA strand breaks. The plasma CCK level was determine d by RIA with OAL-656 antibody. The incidence of nick end-labeling-pos itive cells (apoptotic index) was slightly higher in old rats of both sexes. Apoptosis coincided with the acinar cell loss in old male rats, in which apoptotic index was much greater than that in young animals. The plasma CCK levels produced by bile-pancreatic juice diversion wer e lower in old than in young male rats, whereas no age difference was observed in females. The basal plasma CCK levels were comparable regar dless of age and sex. The pancreatic wet weights were higher in old th an in young rats of both sexes. These observations suggested that alth ough impaired CCK functions in old male rats might have some role in t he increase in apoptosis in the pancreas, the increase in apoptosis co uld not fully explain the attenuated pancreatic response in old rats. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.