Parallel secretion of enzymes by the rabbit pancreas.

1. The purpose of this study was to determine whether or not the secretion of pancreatic enzymes by the rabbit remained proportional (parallel) after acute stimulation. 2. Hourly samples of pancreatic juice were collected from anaesthetized rabbits, each sample being analysed for volume, protein, amylase, trypsinogen and chymotrypsinogen. 3. Four groups of animals were studied for 2 hr before and 2 hr after stimulation with either saline (controls), methacholine, sincalide (C-terminal active octa-peptide of CCK-PZ) or CCK-PZ. 4. Despite a rise in protein output of more than 100% in the hour after stimulation in all experimental groups, there was no change in the specific activity (u./mg protein) of the three enzymes monitored, and the ratios of these enzymes to each other remained constant. 5. These results in the in vivo rabbit confirm our previous observation of parallel secretion in the in vitro rabbit pancreas; they are at variance with other studies in the rabbit (predominantly in vitro but also in vivo) which showed non-parallel secretion after CCK-PZ stimulation. 6. Our results tend to support the theory of mass transport and parallel secretion of pancreatic enzymes though no firm deductions on intracellular events can be made from juice analysis alone.