Pancreatic enzyme activity in obese and lean Zucker rats: a developmental study.

Exocrine pancreatic enzyme activities were measured in female, obese and lean Zucker rats at 1, 3, 6 and 12 months of age. When expressed per 100 g body weight, food intake, pancreatic weight, and activities of trypsin, chymotrypsin and lipase were highest at 1 month and showed a similar decline with age in both obese and lean rats. In contrast, amylase activity declined only in the obese and remained elevated in the lean. Expressed per milligram pancreas, amylase activity was lower in the obese after 3 months, trypsin was elevated in the obese at 6 and 12 months, lipase was lower at 1 month and elevated at 6 months, whereas chymotrypsin did not differ. Hyperinsulinemia was present in obese rats at all ages, and yet amylase levels were reduced. The inability of insulin to elevate amylase activity in obese animals may be a reflection of the insulin resistance of these animals.