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

Despite th e diversity of stu dies on hypo- therrnia, many of its biologic andphysiologic effects are stilI poorly recognized. In this stu dy the effect of hypothermiaon the renin- angiotensin- aldosteroneaxi s wa s explored.Materials and Methods: Ten male albino wi starrats after anesthetizing by chloral hydrate (0.5m1f100gr body weights) were cooled to 25°C. Beforeand just after hypothermia, and once every24 hours for three da ys; serum le vel s of agiotensinI and aldosterone were measured, usingthe radioimmunoassay method. Plasma renin activitywa s also determineded by the stan dardformula for angiotensin determinates at twotemperatures of 4°C and 37°C.Results: Plasma renin activity increased duringhypothermia but then decreased to a level notsignificantly different from basal values. AngiotensinI increased signif icantly in the secondsample taken 24 hours following hypothermia(p O.05) and then decreased to the basal range by72 hours. Serum aldosterone level rose significantlyuntil 48 hours following hypothermia, afterwhich it began to decrease and returned tobasal level.Conclusion: Results of this stu dy advocatethe stimulating effect of moderate hypothermiaon plasma renin activity, angiotensin I and aldosterone.