The Effect of Intermittent Heat Acclimation on Thirst and Body Water Status in Rats
Dr. Christopher Barney
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 SpragueDawley rats were subjected to 4 hours of heat stress (37.5°C) a day, with or without water, for seven days. Control rats were subjected to 4 hours at 25°C with water. On the eighth day the acclimation was tested by exposing all rats to 4 hours at 37.5°C without water, or 4 hours at 25°C with water. Water intake, urine output, and plasma parameters were measured. Plasma parameters consisted of plasma sodium concentration, hematocrit, hemoglobin and plasma protein measurements. There was a significant decrease in evaporative water loss and total water intake from day one to seven and higher percent rehydration and sodium excretion in the heat acclimated groups as compared to a control. There were no significant effects on plasma parameters, or urine output. These data indicate during intermittent heat acclimation plasma volume is conserved at the expense of cellular volume and that the change in water intake with heat acclimation is not the result of alterations in either cellular dehydration or blood volume.
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