Trophic responses of the pancreas differ in aging rats.

We previously have shown that the response of pancreatic lipase and amylase to changes in diet composition is altered in senescent rats. The present study was designed to determine if the trophic response to a defined gastrointestinal peptide stimulus differed in 3-month (young) and 27-month (aging) Fischer rats. Caerulein-secretin, administered every 8 h for 7 days, induced pancreatic hypertrophy and hyperplasia as judged by increases in pancreatic weight, protein, and DNA content in both groups. A significant increase also occurred in the content of trypsinogen, amylase, lipase and the polyamines, putrescine, spermine, and spermidine. To quantify differences in the trophic response between young and aging rats, the ratios of data in the treated animals relative to that observed in controls were determined. Pancreatic weight, protein content, and protein DNA ratio increased significantly more in young than in aging treated animals. DNA also increased more but did not reach significance. Pancreatic trypsinogen and lipase content increased significantly more in younger animals, whereas amylase responses were not different between the two groups. Stimulation of pancreatic putrescine and spermidine was also greater in young than in aged animals. We conclude that trophic responses of the pancreas are altered in senescent rats.