The Effect of Dietary Composition on Pancreatic Enzymes

The ability of the pancreas to alter its external secretion by increasing the output of any given enzyme or enzymes in relation to the predominance of any particular substrate in the diet is a question which has long been debated and never adequately decided. Many years ago it was stated without the submission of adequate evidence that the pancreatic enzymic secretory response to a single meal was adapted to the type of food (l)-e.g., a meat meal elicited a, secretion higher in tryptic activity than a meal low in protein. Today it is generally believed that variations in the principal pancreatic enzymes take place in a parallel manner; in other words, a rise or fall in any one enzyme is accompanied by a coincident change in each of the others. For example, cholinergic drugs elicit a concentrated secretion rich in enzymes, whereas secretin provokes the formation of a dilute juice of low enzyme content; but in any given animal the ratio of concentration of the individual enzymes is the same, regardless of the type of stimulus. Likewise, the pancreatic juice formed in response to various meals may vary in concentration, but not in the relative amounts of the several enzymes. This belief may be true; yet it is still possible that, for example, a diet high in protein after being fed for several days may call forth a secretion richer in trypsin. The parallelism of enzyme concentrations in the course of acute experiments has been established for a number of species, including the dog (Z--4), rabbit (5), cat (6), and human (7). However, the ratio of the concentrations of the various enzymes shows marked variation, both from animal to animal and in the same animal over considerable periods of time. It is not inconceivable that such changes are the result of adaptation to a pronounced and prolonged change in the diet. This possibility has been examined and never adequately confirmed. Two reports from Pavlov’s laboratory (8, 9) state that in pancreatic fistula dogs the protease content increased on a meat diet and subsequently fell off on a high carbohydrate regime. In each case data were apparently obtained on only one animal and the findings were never confirmed. Later investigators devoted their attention to determinations of active and inactive enzymes on the various diets, with inconclusive results (10). More recently the enzyme content of the duodenal drainage of human subjects on various diets has been found to vary in relation to the predominating type of foodstuff in the diet (11) with noticeable differences detectable within a few days. That this problem has not been adequately settled in the past is due to a