Tissue Respiration of Rats Acclimatized to Low Barometric Pressure

¹ From the Department of Physiology, University of Illinois College of Medicine, Chicago, Illinois

Rate of respiration of tissues of male albino rats acclimatized to 18,000 feet simulated altitude for periods averaging 11.2 weeks was determined by Warburg technique under 100% oxygen. Results from 12 experimental animals were compared with 7 controls simultaneously maintained at normal barometric pressure. Acclimatized animals showed no significant changes in growth rate, total metabolic rate or rectal temperature. Hemoglobin values and heart-body weight ratios were elevated. Tissue respiration of brain, small intestine, diaphragm, liver, skeletal muscle, atrium and ventricle was not significantly different from that of controls. Adrenal-body weight ratios were unchanged but increased adrenocortical activity is suggested by a significant increase in adrenal qO₂. Respiration of acclimatized kidney slices was significantly reduced. It is concluded that generalized adaptation of cellular metabolism to hypoxia does not occur in acclimatization but that changes may be demonstrated in tissues specifically involved in the adaptation process.