Endocrine pancreatic morphology and function in exocrine insufficiency in rats

Exocrine pancreatic insufficiency was induced in rats by injection of oleic acid into the pancreatic duct. Six weeks after a single injection of 50 microliters oleic acid, the exocrine tissue was reduced by 98%. The islets of Langerhans remained intact and showed no changes in the relative distribution of beta-, alpha-, D-, and PP-cells. In rats fed ad libitum, plasma insulin levels and pancreatic insulin content did not differ between oleic acid-treated animals and controls. The dynamic insulin response was evaluated in the isolated perfused pancreas. The biphasic pattern of insulin release after stimulation by glucose was preserved. The half-maximal (10 mM) glucose-induced insulin release was reduced to 49% after onset of exocrine atrophy. After stimulation of insulin secretion by a maximal glucose load (20 mM), the insulin output from the perfused pancreas was reduced to 56%. A reduction in insulin release to 24% occurred with respect to the arginine (15 + 10 mM glucose)-stimulated secretion. To evaluate the significance of these findings in intact animals, glucose tolerance tests were performed. There were no differences between oleic acid-, saline-, or untreated animals with respect to serum glucose or plasma insulin levels during the oral glucose tolerance test. The insulin response after intravenous glucose in oleic acid-treated rats was not statistically different from controls. Nevertheless, the serum glucose levels in rats with exocrine atrophy were above controls, indicating a slight impairment of glucose tolerance.