Effect of Repeated Acute Exposures to High Altitude on Longevity in Rats

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Abstract
53 male and female rats were exposed to 18,000 ft. simulated altitude 4 hrs. daily from 14-540 days of age, and observations were continued until death. The exposed rats lived as long as unexposed controls. There was a proportionate increase in the hematocrit values and in the hemoglobin (Hb) content of the blood of exposed rats, with males reaching higher levels (hematocrit value 78, Hb 23 g./100 cc.) than females (hematocrit value 70, Hb 20 g./100cc). No significant increase was noted in the wt. of the heart and adrenal glands and there was no abnormal thymus atrophy. In histopathologic study of 82 additional exposed rats some showed fatty degeneration and hemosiderosis of the liver and kidney and some had significant fatty changes in the renal vessels. There was general congestion with increase in the size of the renal glomeruli, apparently due to capillary engorgement. Because of the increase in hematocrit values, there is an increase in the capillary and erythrocyte surface areas per unit of plasma. The importance of these changes in the diffusion of gases and other substances to and from the blood stream during exposure to high altitude is discussed.
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