Relationship between thermogenic drinking and plasma renin activity in the rat

The spontaneous water intake of rats increases when they are transferred abruptly from a cold (5 degrees C) to a neutral (25 degrees C) environment. This has been termed thermogenic drinking. Treatment of cold-acclimated rats with SQ 14,225, an angiotensin converting enzyme inhibitor, at 10-50 mg/kg of body weight prior to removal from cold, inhibited the thermogenic drinking response in a dose-dependent manner. Plasma for determination of plasma renin activity (PRA) was obtained by cardiac puncture from methoxyflurane anesthetized rats maintained chronically at both 25 degrees and 5 degrees C. In addition, plasma was obtained from cold-acclimated rats 15 min after removal from 5 degrees to 25 degrees C. PRA values were 2.2 +/- 0.4 (S.E.) ng/ml/h for control rats; 1.9 +/- 0.8 ng/ml/h for cold-acclimated rats and 8.5 +/- 1.7 ng/ml/h for cold-acclimated rats removed from cold for 15 min. Thus, PRA was significantly increased in rats removed acutely from cold. These data suggest that thermogenic drinking may be mediated by the renin-angiotensin system.