Water content, water turnover, and water half-life during cold acclimation in the rhesus monkey.

Abstract

The purpose of this study was to examine the effects of cold acclimation on the dynamics of body water in primates. Six male rhesus monkeys were acclimated for 35 days at 6 °C. Water turnover rate (WTR), biological half-life (t1/23H2O), and total body water (TBW) were estimated by the tritium dilution method. A reduced water intake during the 1st week of cold acclimation was associated with a decrease in water balance (total water input minus WTR). Both drinking and total water input were decreased throughout the cold exposure. WTR was significantly decreased during the last 3 weeks of cold exposure in spite of an increased caloric consumption, which, in a thermoneutral environment, generally is associated with an increased WTR. Biological half-life for tritium showed a significant average increase during the cold stress. TBW in relation to body weight was increased during the first 2 weeks of cold exposure and had decreased to its lowest level by day 22. Calculations of TBW were independent of whether the radioactive decay curve was obtained over short (minutes) or long (days) time intervals and independent of the degree of acclimation. The major adjustments in water content and water metabolism occurred within 2 weeks of continuous cold exposure at 6 °C. The data suggest that the rhesus monkey may be an adequate primate model for studies of body fluid adjustments induced by chronic cold exposure in primates in general, including man.