Changes in Pancreatic Enzymes as a Function of Diet in the Chick. ∗

The phenomena of enzyme induction and repression are very well established in microorganisms, yet for vertebrates and mammals these have not been thoroughly investigated. The ratio of pancreatic enzymes is variable among species( 5 , 9 , 12 , 13 ). Determinations of enzymes in homogenates of pancreata from rats fed either starch-rich or casein-rich diet show that specific activities of amylase and chymotrypsin reflect the starch and casein content of the diet( 15 ). In chicks, the pancreata enlarge when unheated soybean meal is consumed. These pancreata show depletion of zymogen granules to a greater extent than the corresponding pancreata from chicks fed autoclaved soybean meal diet. This histological evidence was confirmed by chemical analysis ( 1 ). We investigated the rate of synthesis of enzymes by the pancreas of chickens after an adaptation period of 4 weeks on either unheated or autoclaved soybean meal.

Experimental. Two groups of chicks were fed either unheated or autoclaved soybean meal for 4 weeks. The composition of the basal diet was essentially that used by Dal Borgo( 4 ). After this adaptation period, the chicks were fasted: 3 birds of each group were sacrificed at 0, 6, 12, 16, and 22 hours after the start of fast. After 16 hours of fasting, each group was divided into 2 subgroups, one of which was fed the same diet as before the fast. and the other the alternate diet. Three chicks from each of the 4 subgroups were sacrificed after 2 and 6 hours on the diet. The pancreata were excised aid weighed (after removal of extraneous tissue), then stored at −15°C.

Trypsin and chymotrypsin were ashayed using p-toluene-sulphonyl-L-arginine-methyl ester (TAME) and N-Benzoyl-L- tyrosine ethyl ester (BTEE), respectively ( 7 ). Amylase activity was determined by the 3,5,-(dini-trosalicylate method( 3 ). Protein in the pancrcatic homogenates was determined by measuring the absorbancy at 280 and 260 μ to correct for nucleic acids ( 10 ).