Abstract: Objective To investigate the effect of aldosterone （Ald） on calcineurin （CAN） activities of the vital organs and plasma NO, Ang Ⅱ and ET-1 levels in rats and the role of aldosterone on the calcineurin-dependent signal transduction pathways. Methods Twenty-one male Wister rats were divided into 3 groups randomly: Ald group（n=7） with Aid 18μg/d, i. p for 4 weeks; cyclosporine A（CsA） group（n=7） with Ald+CsA 5mg/kg·d, i. p for 4 weeks; and contral group（n=7）. The plasma concentrations of Aid, angiotensin Ⅱ（Ang Ⅱ） and endothelin（ET-1） were determined by the radioimmunoassay. The blood level of NO was assayed by the nitrate assay. CaN activity was measured by using PNPP as substrate. Results Compared with contral group, the tissue CaN activities in heart, spleen, kidney, lung, brain, liver of Aid rats was increased by 147%, 65%, 38%, 100%, 43%, 50%, respectively （All P＜0.05） and the blood NO₃^- concentration of Ald rats was decreased（P＜0.05）. Cyclosporine A reverses the increases of CaN activities induced by aldosterone in these organs and tissues（P＜0.05） and increased the blood NO₃^- concentration. The plasma concentrations of Aug Ⅱ and ET-1 of three groups did not differ significantly. Conclusion Mediating the calcineurin-dependent signal transduction pathways, aldosterone upregulate calcineurin activity of the vital organs and decrease the plasma NO level of rats.