Effect of dietary change upon the amylase and trypsin activities of the rat pancreas

Most of the reports on enzyme adaptation, by ourselves and other workers, have been concerned with the enzymes of micro-organisms.We have, however, also made a few observations on rats, some of which have been concerned with digestive enzymes (e.g.Lawrie & Yudkin, 1949; Roberts & Yudkin, 1961).The work to be described was carried out as a confirmation and extension of that reported by Ivy and his colleagues (Grossman, Greengard & Ivy, 1942-3, 1944).These workers measured the activity of three pancreatic enzymes : amylase, trypsin and lipase.Our own work is concerned with the first two.Grossman et al. in their main experiment fed rats for 21 days on one of four purified diets, in which the chief differences were in the proportion of carbohydrate as starch, protein as casein and fat as lard.The control diet contained 47% starch, 18 % casein and 18 % fat.When the starch was increased to 67 % of the diet, there was a 40 yo increase in the amylase activity of the pancreas and a 50 yo fall in the trypsin activity.When the casein was increased to 67% of the diet, there was a 20% fall in amylase activity and a threefold increase in trypsin activity.When the lard was increased to 54 % of the diet, there was a 65 % fall in amylase activity and no change in trypsin activity.It should perhaps be added that the four diets differed in the proportion of all three major constituents, so that, for example, the high-carbohydrate diet contained 67 % starch, 15 % casein and 27 % lard.In later experiments, the same workers showed that a substitution of the starch in the control diet by glucose increased amylase activity by about 20%, but did not affect trypsin activity (Grossman et al. 1944).A substitution of the casein by hydrolysed casein decreased trypsin activity by about 20 %, but did not affect amylase activity.The daily injection of protamine zinc insulin into rats given the control diet resulted in a 30 % fall in amylase activity, but did not affect trypsin activity.