Abstract: AIM: To investigate the expression of myocardial calcineurin inhibitor (Cain) in renal hypertensive rats and the changes of active related factors in plasma. METHODS: Twenty one male Wistar rats were randomly divided into three groups (n=7): sham operation group, operation group treated with traditional one kidney and one clamp operation, and spironolactone group treated with spironolactone ［20 mg/(kg·day)］. Angiotensin II (AngII) and Ald levels in plasma were determined by radioimmunoassay. The expression of Cain in myocardium was determined by Western blot. RESULTS: Ald and AngII levels, expression of Cain and activity of calcineurin in myocardium all increased in operation group compared with those in sham operation group. AngII level markedly decreased in spironolactone group compared with that in the operation group. Expression of myocardial Cain level and calcineurin activity also decreased significantly. CONCLUSION: Internal Ald induces cardiac hypertrophy through a calcineurin-dependent signal pathway. The expression of internal Cain may be controlled by the activity of calcineurin.