Measuring total plasma amino acid concentrations as a test of exocrine pancreatic function.

Endogenous and exogenous stimulation of the pancreas was studied to determine whether changes in protein output could be linked to decreased total plasma amino acid concentrations. In fasted rats, diversion of pancreatic juice resulted in a transient increase in protein output and a linked fall in total plasma amino acid. In fed animals, however, diversion of juice did not result in any change in protein output or total plasma amino acid concentrations, although protein output was two-fold greater than in fasted animals. Similarly, after atropine treatment, diversion of juice failed to result in any change in protein output or total plasma amino acid in either fed or fasted animals. Stimulation of the gland with increasing doses of cholecystokinin ranging from 1.25 to 10.00 Crick Harper Raper Units, resulted in dose response increases in protein output and corresponding dose response falls in total plasma amino acid concentrations. Maximum decrease in total plasma amino acid concentrations was seen at 50% from the baseline with 5.00 Crick Harper Raper Units of cholecystokinin. These results show that with exogenous and endogenous stimulation in fasted animals, a highly significant, inverse relationship exists between protein output and total plasma amino acid. This relationship is the basis for a reliable, non-invasive test of pancreatic function that allows free mobility, although a period of fasting is required in order to increase the sensitivity of the test.