Effects of Enviromental Temperature on Cardio-Vascular System in Experimental Animals

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To elucidate effects of environmental temperature on atrial natriuretic peptide (ANP) in experimental animals, the blood pressure (BP), heart rate (HR) and body temperature (BT) in rats under hot (33ﾟC) and cold (15ﾟC) environmental conditions were measured by a biotelemetridc system. Further, the ANP levels of auricular cardiocytes and plasma were examined by immunohistochemistry, electron microscopy, and radioimmunoassay (RIA) in rats under both environmental conditions. (1) Mean arterial BP,HR,BT : there is no change of HR,but BP and BT were significanlty increased under hot condition compared to the control level as time went by. Then those parameters were returned to normal levels after two or three hours when hot condition was changed to normal environmental condition (22ﾟC). There were no changes in BP and BT,but HR was significantly increased in cold condition compared to the control level as time went by. Then HR was returned to normal levels after one hour when cold condition … More was changed to normal condition. (2) Plasma ANP concentration : the concentration in hot condition was significantly higher than that in normal condition. When hot condition was changed to normal environment, the concentration was returned to control level after three hours. The concentration was significantly higher after only one hour in cold condition than that in normal condition. (3) Immunohistochemistry and ultrastructure : NP immunoreactivity (IR) in the auricular cardiocytes under hot condition was stronger than that in normal condition, and was strongest after 24 hours under hot condition. Then the IR was returned to the control level after three hours when hot condition was changed to normal environmenta. In cold condition, the IR was stronger after only one hour than that in normal condition. Ultrastructurally, the number of ANP-granules in the cardiocytes. with the stronger ANP-IR was greater that that with the weaker IR.The present study suggests that the circulating ANP and cardio-vascular systems are greatly influenced by hot environmental condition. Less