ADMINISTRATION OF ANTERIOR PITUITARY GROWTH HORMONE TO RATS DURING COLD EXPOSURE

Abstract

Male, growing rats were injected daily with anterior pituitary growth hormone (3 mg/100 g body weight) and fed ad libitum for 7 days at environmental temperatures of 22 °C and 2–3 °C. Body weight gain, nitrogen retention, and four liver enzyme activities were measured. As observed previously, cold exposure retarded body weight gain and decreased nitrogen retention despite an increased food intake. These effects of cold were not eliminated by administration of growth hormone. The increased activities of liver arginase, alanine-glutamic transminase, and phosphate-activated glutaminase consequent upon cold exposure were not significantly affected by growth hormone although, at 22 °C, growth hormone decreased the activities of liver arginase and alanine-glutamic transaminase. Cold exposure eliminated the lowering effect of growth hormone on liver glutamic acid dehydrogenase activity observed at 22 °C. It is concluded that, under these conditions, growth hormone does not overcome the protein catabolic effects of cold exposure but rather, cold exposure eliminates the protein anabolic effects of the hormone.