Effects of Abrupt Temperature Changes on Excretion Characteristics of Rats Acclimated to Cold, Neutral or Hot Environments

¹ From the Clayton Foundation Biochemical Institute, University of Texas, Austin, and the Department of Physiology and Biophysics, School of Aviation Medicine, USAF, Randolph Air Force Base, Texas

The responses of acclimated rats (heat, 35°C; neutral, 24°C; or cold, 3°C) to abrupt temperature changes (24-hr. exposure with fasting) are compared. Variables studied include weight loss, rate of fasting weight loss regain, water intake, urine volume, urinary Na, K, Ca, Mg, PO₄, urea, uric acid, creatinine, creatine, taurine, ß-alanine, glycine, -alanine, valine + methionine, serine, threonine, tyrosine, glutamic acid, aspartic acid, lysine, arginine and histidine. As compared to the neutral controls, most of the variables of the heat- and cold-acclimated rats were different under all conditions tested. Despite adaptive changes induced by the prior treatments, however, the changes directly attributable to abrupt environmental shifts were somewhat similar for the majority of the variables to those of the controls. Other variables in the cold-acclimated group tended toward nonresponsiveness, while the the heat-acclimated group tended toward overresponsiveness. Return to the neutral environment did not always result in a normalization, though the tendency was often in this direction.