Influence of captopril on intracellular free calcium concentration and involved ion channels mechanisms in cardiac myocytes of the neonatal rat undergone anoxia-reoxygenation injury

AIM:To observe the influence of captopril on intracellular free calcium concentration([Ca 2+] i)and the involved ion channels mechanisms in cardiac myocytes of the neonatal rat undergone anoxia-reoxygenation injury.METHODS:The anoxia-reoxygenation model in cultured neonatal rat ventricular myocytes was established.Groups were divided into ① normal;② anoxia-reoxygenation;③anoxia-preconditioning(5 min anoxia+5 min reoxygenation);④ captopril preconditioning.Flou-3 /AM loading and flow cytometry technique were used to observe the [Ca 2+]i,and whole-cell patch clamp technique was used to record the L-type calcium current and Na+/Ca 2+ exchange current.RESULTS:① Compared to normal group,[Ca 2+]i in anoxia-reoxygenation group was increased significantly(789.42±9.05 vs 414.08±37.40,P0.01),L-type calcium current density was decreased(P0.01),the current-voltage curve was moved up,the inactivation curve was moved left and Na+/Ca 2+ exchange current was increased in anoxia-deoxygenating.② Compared to anoxia-reoxygenation group,anoxia and captopril preconditioning resulted in a significant decrease in [Ca 2+]i(593.84±5.06,507.08±31.89 vs 789.42±9.05,P0.01),and a significant increase in L-type calcium current density(P0.01),the current-voltage curve was moved down,the inactivation curve was moved right and Na+/Ca 2+ exchange current was decreased ③ Compared to normal oxygen condition,the anoxia and captopril precondition resulted in a lightly increase in [Ca 2+]i(507.08±31.89 vs 414.08±37.40,P0.05)and Na+/Ca 2+ exchange current.④ Compared to anoxia-preconditioning group,captopril-preconditioning resulted in no significant difference in all the markers mentioned above.CONCLUSIONS:The anoxia-reoxygenation injury in cardiac myocytes results in [Ca 2+]i abnormal increase and calcium overload by increasing Na+/Ca 2+ exchange current.Late preconditioning in cardiac myocytes is triggered by transient and repeated anoxia and captopril,which slightly increases Na+/Ca 2+ exchange current and [Ca 2+]i and restraines the abnormal increasing of Na+/Ca 2+ exchange current and calcium overload induced by subsequenced anoxia-reoxygenation injury,so it plays an delayed protective role in cardiac myocytes.L-typed calcium passage is not involved in calcium overloaded and late preconditioning of calcium in myocytes during reperfusion.