High Altitude and Protein Metabolism in the Rat 1

Summary Activities of hepatic arginase and arginine synthetase and incorporation of alanine or glutamic acid into tissue proteins were studied in rats exposed acutely or chronically to an altitude of 14,110 feet. Compared to the controls, activities of the two enzymes were significantly increased after 2 days but not after 30 days at altitude. By way of contrast, a decrease in amino acid incorporation into liver, spleen, duodenal, and adrenal proteins was observed in rats exposed to altitude for two days. Altitude exposure for 30 days had no effect on amino acid incorporation into tissue proteins. The data demonstrate an increase in protein catabolism during an acute exposure to hypoxia.