Effects of Thermal Conditioning on Metabolic Responses of Rats to Altitude

Abstract

The metabolic responses of rats acclimated to different temperatures (3°, 24° and 35°C) were compared during a 24-hour fasting exposure to low barometric pressure (380 mm Hg). Determinations included fasting weight loss, water intake, urine volume and urinary excretion of Na, K, Mg, Ca, PO₄, urea, uric acid, creatinine, creatine, taurine, ß-alanine, glycine, α-alanine, valine + methionine, serine, threonine, tyrosine, glutamic acid, aspartic acid, lysine, arginine and histidine. Since the altitude tests were made at a neutral temperature (25°C) the altitude responses, per se, were determined by comparing the ground and altitude responses of each acclimated group at neutral temperatures. These comparisons revealed that the acclimated state of the rats exercised a strong influence on the altitude response for most of the variables. There were significant intergroup differences in this response for all variables except phosphate, urea, taurine, valine + methionine, serine, histidine and the Mg/Ca ratio.