OBJECTIVE To observe the influence of captopril on in tracellular free calcium concentration([Ca²⁺]_i) and Na⁺/Ca²⁺ exchange current in the cardiac myocytes of the neonatal rat undergone anoxia-reoxygenation injury.METHODS The anoxia-reoxygenation models were developed.The cultured ventricular myocytes of neonatal rat were established and divided into normal,anoxia-reoxygenation and captopril preconditioning groups.By using Flou-3/AM loading and flow cytometry technique,the [Ca²⁺]_i was observed,and whole-cell patch clamp technique was used to record the Na⁺/Ca²⁺exchange current.RESULTS ①Compared with normal group,[Ca²⁺]_i and Na⁺/Ca²⁺ exchange current in anoxia-reoxygenation group were increased significantly(P<0.01).②Compared with anoxia-reoxygenation group,the captopril precondition group resulted in a significant decrease of [Ca²⁺]_i in a concentration dependent manner,and Na⁺/Ca²⁺ exchange current was also decreased.③Compared with normal oxygen condition,the captopril precondition group resulted in a light increase of [Ca²⁺]_i and Na⁺/Ca²⁺ exchange current.CONCLUSION The anoxia-reoxygenation injury in cardiac myocytes resulted in an abnormal increase of [Ca²⁺]_i by increasing Na⁺/Ca²⁺ exchange current.Late preconditioning in cardiac myocytes is triggered by captopril which slightly increased Na⁺/Ca²⁺ exchange current and [Ca²⁺]_i,and restrained the abnormal increasing of Na⁺/Ca²⁺ exchange current and calcium overload induced by subsequenced anoxia-reoxygenation injury.