The Effect of Moderate Hypothermia on Renin- Angiotensin- Aldosterone System in Male Rats

Despite the diversity of studies on hypothermia, many of its biologic and physiologic effects are still poorly recognized. In this study the effect of hypothermia on the renin- angiotensin- aldosterone axis was explored. Materials and Methods: Ten male albino wistar rats after anesthetizing by chloral hydrate (0.5 m1/100gr body weights) were cooled to 25oC. Before and just after hypothermia, and once every 24 hours for three days; serum levels of agiotensin I and aldosterone were measured, using the radioimmunoassay method. Plasma renin activity was also determineded by the standard formula for angiotensin determinates at two temperatures of 4oC and 37oC. Results: Plasma renin activity increased during hypothermia but then decreased to a level not significantly different from basal values. Angiotensin I increased significantly in the second sample taken 24 hours following hypothermia (p<0.05) and then decreased to the basal range by 72 hours. Serum aldosterone level rose significantly until 48 hours following hypothermia, after which it began to decrease and returned to basal level. Conclusion: Results of this study advocate the stimulating effect of moderate hypothermia on plasma renin activity, angiotensin I and aldosterone.