Growth, protein utilization, and secretion of pancreatic enzymes by rats in response to elevated levels of dietary protein

Abstract

Rats were fed diets containing 15, 30, 45, or 60% casein for 30 days. The weight gains of rats fed diet containing 30% casein were higher (P<0.05) than that of rats fed 15, 45 or 60% casein diets. Food intake was similar in the 15% and 30% casein diets and lower in the 45% and 60% casein diets. Blood plasma urea level increased in parallel to the increase in dietary protein and was inversely related to PER. Water intake increased with the increase in dietary protein level. The relative weights of the pancreas and kidneys increased with the increase in protein level as did the activities of the digestive enzymes. However, while trypsin and chymotrypsin activities were increased both in the pancreas and in the intestine, lipase was increased only in the intestine and amylase only in the pancreas. The response to elevated dietary protein, as shown by the levels of digestive enzymes excreted in the feces, was very marked in the first week and was smaller and inconsistent later on. The digestibility of casein was related to trypsin and chymotrypsin activities in the pancreas and small intestinal contents.