Hormonal factors in the rat's tolerance to altitude.

Abstract

The survival period of adrenalectomized rats, which are less tolerant than normal rats to reduced barometric pressure (equiv. to altitude of 27,800 ft), can be extended when the animals are pretreated with adequate amounts of cortisol. Pretreatment of adrenalectomized animals with somatotropin (0.5 mg/100 g body wt.) did not have any significant effect on tolerance to simulated altitude, but when somatotropin was administered simultaneously with a subeffective dose of cortisol, tolerance to altitude was significantly increased. Thyroidectomy did not have a beneficial effect on survival of adrenalectomized animals, but pretreatment of adrenalectomized-thyroidectomized rats with 3 mg cortisol, which is inadequate to protect the adrenalectomized animal against exposure to simulated altitude, significantly increased survival rate. A possible mechanism whereby lesser amounts of cortisol are effective in prolonging survival of thyroidectomized-adrenalectomized rats exposed to low barometric pressure may be a decrease in catabolism of the steroid in hypothyroid animals.