The Effects Of Intermittent Heat Acclimation On Water Balance In Rats

Jacob Johnson
Amanda Beck
Ellen Ray
Veena Janardan
Christopher C. Barney, Hope College

(Meeting Abstract Supplement) 1115.18


Heat exposure can lead to thermal dehydration in rats, as they use saliva spreading for evaporative cooling. The effects of heat acclimation in rats on thermal dehydration and subsequent water intake are not well understood. In this study, male Sprague-Dawley rats were exposed to 37.5°C (Intermittent Heat Acclimation - IHA) with or without water or to 25°C with water for 4 hours/day for 7 consecutive days. Water losses and intakes were determined during the exposure period and a 3 hour drink period on days 1 and 7. On day 8, rats from each experimental group were exposed to either 25°C with water or 37.5°C without water for 4 hours and then blood samples were taken for estimation of cellular and extracellular dehydration. Heat exposure increased water intake both during and after the exposure and having access to water during heat exposure increased evaporative water loss but did not alter urine output. IHA decreased evaporative water loss during heat exposure, while not altering urine output during or after heat exposure. IHA also increased water intake in the heat and decreased drink period water intake and total water intake without changing blood indicators of cellular or extracellular dehydration. IHA reduces evaporative water loss during heat exposure leading to a subsequent reduction in total water intake without altering physiological thirst drives. Supported by a NSF REU Site Award (DBI-0754293)°