METABOLIC EFFECTS OF THREE DIETARY PROTEIN LEVELS FED ISOCALORICALLY TO COLD-EXPOSED RATS

Abstract

Male albino rats were fed isocalorically on diets containing 5%, 20%, and 40% protein (casein) and 10% corn oil by weight at environmental temperatures of 22 °C and 2 °C. Since the 5% protein fed group consumed less than normal amounts of food, consequently the food intake of all groups was moderately restricted. Measurements were made of urinary excretion of nitrogen, potassium, sodium, phosphorus, and creatinine, of blood levels of glucose, urea, amino nitrogen, packed cell volume, and serum total proteins and of total body content of protein, water, and crude fatty acids. Metabolic effects of dietary protein level were readily apparent at both environmental temperatures. Unlike earlier studies with ad libitum and severely restricted feeding, superimposition of cold exposure did not eliminate metabolic differences among groups. As observed in previous studies, reduction of dietary protein level from 20% to 5% had a deleterious effect in cold-exposed rats. In the present study no beneficial effects due to increasing dietary protein level from 20% to 40% were observed.