Influence of plasma amino acid level on urine volume in the alligator

¹ Departments of Biochemistry and Pharmacology, Louisiana State University School of Medicine, New Orleans, Louisiana

Growth hormone, hydrocortisone, and a mixture of the two were injected daily into small alligators for periods up to 2 weeks. Although plasma amino acid levels increased only slightly after either growth hormone or hydrocortisone, injection of the combined hormones doubled the concentrations. In all cases increases in plasma amino acids were associated with an augmented renal ammonia synthesis and an increased urine volume. When the degree of hydration was maintained at a nearly constant level, the urine volume was directly related to the quantity of amino acids available for renal deamination. Insulin, a hormone which lowers the concentration of extracellular amino acids, decreased the rate of renal ammonia synthesis and therefore the rate of urine flow. The oliguria produced by insulin could be counteracted by the injection of glycine, a known precursor of urinary ammonia. Evidence is presented which suggests that in the "diabetes" caused by a combined injection of growth hormone and hydrocortisone, protein catabolism is enhanced and fat catabolism is inhibited. A negative nitrogen balance occurred as a result of the delivery of more amino acids for renal deamination.