Metabolism of human serum albumin in man during acute exposure to high altitude (14,100 feet).

The effect of high altitude exposure on protein metabolism in man has not been fully investigated. In a recent study of eight sea level residents (1), the concentration of plasma total protein and of the specific proteins thyroxine-binding globulin and ceruloplasmin was noted to be increased during the first 2 weeks of exposure to high altitude. Since the electrophoretic distribution of the plasma proteins was unchanged, the observations were interpreted as resulting from marked water loss from the intravascular compartment. In contrast to these changes, the concentration of thyroxine-binding prealbumin (TBPA) was decreased dur-ing this period. Alterations in the metabolism of this plasma protein may be manifest rapidly by changes in its concentration due to its rapid rate of metabolism (2, 3). Thus, the reduced con-centration of TBPA noted at high altitude was interpreted to reflect possible changes in plasma protein synthesis or degradation in this environ-ment that had been masked by the dehydration of the intravascular compartment. In the present investigation, the turnover of `31I-labeled albumin was studied in five subjects during a control period at 5,280 feet and for eight days at 14,100 feet. The method of data analysis allowed an independent estimate of the daily rate of albumin synthesis and degradation during the experimental period. These observations were correlated with simultaneous measurements of gross nitrogen balance, TBPA concentration, and various indexes of thyroid function. * Submitted for publication March 3, 1966; accepted