THE RÔLE OF THE ADRENAL CORTEX IN ANOXIA: THE EFFECT OF REPEATED DAILY EXPOSURES TO REDUCED OXYGEN PRESSURE

Abstract

Young [male] rats, exposed repeatedly to a pressure equivalent to 18,000 feet altitude for four hours daily, 5 days a wk. over a period of 5 to 8 weeks, maintained a normal rate of growth and appeared to tolerate the exposures rather well. The majority of a group of young male rats, exposed in a similar manner to a pressure equivalent to 27,000 ft. altitude tolerated the exposures but failed to gain wt. at a normal rate during the days on which exposures were made. Adaptation to repeated short exposures to low pressure was associated with a, increase in hematocrit values (vol. % of packed red blood cells); b, increased wt. of adrenals. The fasting levels of blood sugar and liver glycogen of animals exposed repeatedly to low barometric pressure were normal or lower than normal. Adrena-lec-tomized rats were unable to withstand repeated exposures to low barometric pressure unless treated with adrenal cortical hormone. Young [male] rabbits tolerated repeated daily exposures (4 hrs., 7 days a wk., for 5 wks.) to reduced barometric pressure equivalent to 18,000 ft. altitude. Such animals did not tolerate repeated exposures to a pressure equivalent to 25,000 ft. altitude. Death of animals was associated with hemorrhages into the lungs and herniation of distended loops of intestine into the thoracic cavity. Most of the fatalities occurred during the 1st or 2d day of the exposure. Repeated exposures to low pressure equivalent to either 18,000 or 25,000 ft. altitude were accompanied by a striking but temporary delay in rate of growth. A slight reduction in the conc. of Na, Cl and in the CO2 combining power of the serum was noted in rabbits exposed repeatedly to a pressure equivalent to 25,000 ft. altitude. The carbohydrate levels of rabbits exposed repeatedly to low pressure were reduced considerably below those of unexposed controls. Repeated exposures to low pressure were accompanied by a, increase in O2 capacity of the blood; b, increase in hematocrit values (vol. % of packed red blood cells); c, increase in adrenal wt.; d, decrease in thymus wt. Normal dogs exposed repeatedly to low barometric pressure equivalent to 25,000 ft. altitude soon developed anorexia and wt. loss. Normal wt. was not restored for weeks after exposures had been discontinued. Adre-nalectomized dogs maintained on desoxycorticosterone acetate did not tolerate repeated exposures to low barometric pressure equivalent to 25,000 ft. altitude. No significant changes in serum electrolyte conc. were observed in dogs exposed repeatedly to low pressure. The great increase in the number of red blood cells, hematocrit value and O2 capacity of the blood was the most striking change which was observed in normal dogs exposed repeatedly to low pressure.