ABSTRACT
OBJECTIVE To observe the effect of natrin from Naja naja atra(Chinese cobra)on intracellular free calcium overload,and to discuss the protective effect and the possible mechanism of natrin on myocardium calcium(Ca2+)and potassium(K+)ion channels in the primary cardiomyocytes of SD neonatal rats. METHODS The primary cardiomyocytes of SD neonatal rats were used,which were respectively pretreated with natrin 5,25 and 125 mg · L-1 for 24 h before injury was induced by H2O2 0.3 mmol · L- 1. The dynamic variation of intracellular calcium was monitored by laser confocal microscopy using Fluo-3 as Ca2+fluorescence probe. Additionally,the cardio myocytes of neonatal rats were pretreated for 24 h using different concentrations of natrin 5,25,125 mg · L-1 and verapamil 5 nmol · L-1,followed by exposure to H2O2 0.3 mmol · L-1 for 15 min. Then,the mRNA expressions of calcium channels subunits Cav1.2,Calm,RyR2 and potassium channel Kir6.2 were analyzed by FQ-PCR method. RESULTS Laser confocal microscopy revealed that H2O2 obviously caused calcium overload in cardiomyocytes, giving rise to 49.37% fluorescence increase in intracellular calcium compared with the control group(P<0.01). However,natrin 5,25 and 125 mg·L-1 resulted in 27.52%, 12.71% and 5.15% fluorescence increase in intracellular calcium,respectively,compared with the control group(P<0.01). Moreover, the PCR results showed that the mRNA expressions of Cav1.2, Calm and RyR2 in the myocardial cells treated with H2O2 were increased 2.78,2.26,and 5.34 times as compared with the control group,while Kir6.2 displayed a 1.79-fold expression level(P<0.01). By contrast, the combination of natrin and verapamil significantly decreased the mRNA expression of Cav1.2,Calm and RyR2,compared to the H2O2-treated group(P<0.01). Meanwhile,the expression of Kir6.2 was considerably higher than that of the H2O2-treated group(P<0.05). CONCLUSION Natrin can reduce the intracellular calcium overload of cardiomyocytes induced by H2O2 and shows a protective effect against oxidative damage for cardiomyocytes. The possible mechanism is that natrin can decrease the mRNA expression of Cav1.2,Calm,RyR2 and increase the expression of Kir6.2 of the H2O2-induced cardiomyocytes.