The interrelationships of the pancreatic enzymes.

Progress report The interrelationships of the pancreatic enzymes The quantitative interrelationships between the different functional types of pancreatic enzymes has been the subject of much experimental investigation , but the results are conflicting and the inferences remain controversial. Recent improvements in techniques have provided new and more reliable means of measuring enzyme activities and it therefore seems pertinent to review the current state of knowledge about the factors which determine selective production of the pancreatic enzymes. Pavlovl, quoting the studies of his pupil Walther in dogs, described rapid 'adaptive' changes in the amounts of individual pancreatic enzymes secreted in response to changes in the predominant type of food in a single meal. Later studies supported Pavlov's hypothesis that the production of individual enzymes, or groups of enzymes, could be selectively modified, but changed the emphasis by indicating that adaptation of pancreatic enzyme secretion might require prolonged dietary modification, for periods ranging from hours to weeks2'3'4. The converse hypothesis, that pancreatic enzymes were secreted 'in parallel', was proposed during the early years of the present century by Babkin5,6 on the basis of experiments in dogs with pancreatic fistulae and was later supported by studies of pancreatic secretion in other species, including man. In order to disentangle the current state of the evidence for the two conflicting hypotheses, the interrelationships between the pancreatic enzymes within the pancreatic-secreting cells, in the secreted juice, and within the small intestinal lumen are considered separately, since different factors determine the relative increase or decrease of individual enzymes or groups of enzymes in the three compartments. Interrelationships of Enzymes within the Pancreatic Acinar Cells While the original hypotheses of 'dissociated' or 'parallel' secretion of enzymes referred to the enzyme content of pancreatic juice, the interrelationships of the enzymes within the pancreatic acinar cells has been studied because the enzyme content of the zymogen granules has been considered to represent 'preformed' pancreatic juice3. Using immunological staining techniques, Marshall7 found uniform intra-cellular distribution of chymotrypsinogen and procarboxypeptidase in the pancreas. Keller, Cohen, and Neurath8 also demonstrated uniform incorporation of radioactively labelled arginine into trypsinogen and chymo-trypsinogen at all stages of synthesis and storage, although incorporation of 398