Protective Effects And Mechanisms Of Polarizing Cardioplegia On Isolated Cardiomyocytes Of Rat

Objective To investigate the protective effects and mechanisms of polarizing cardioplegia with sodium channel inhibitor tetrodotoxin (TTX) on isolated cardiomyocytes of rat.Methods Beating ventricular myocytes were isolated from adult rat hearts by enzymatic dissociation, and randomly created in Group Base, Group STH2 and Group TTX. Group Base was only treated with K-H solution. Both Group STH2 and Group TTX were treated with STH2 and TTX cardioplegia respectively, and the arrest/re-beating cell models imitating ischemia-reperfusion injury were established. All three groups were imaged by laser scanning confocal microscope with fluorescent probe for measuring [Na+]i and [Ca2+]i of cardiomyocytes in different stage. The beating status and morphology of cardiomyocytes were observed under inverted microscope. Results The elevation of [Na+]i and [Ca2+]i of cardiomyocytes during arrest in Group TTX was significantly lower than that in Group STH2. [Na+]i and [Ca2+]i in both Group STH2 and Group TTX after re-beating were higher than those in Group Base (P＜0.01), but [Na+]i and [Ca2+]i in Group TTX were significantly lower than those in Group STH2(P＜0.01). There was no difference in beating rate between Group STH2 and Group TTX(P＞0.05). Active cardiomyocytes with normal morphology in Group TTX after re-beating were more counted than those in Group STH2 (P＜0.01). Conclusion Compared with conventional depolarizing cardiopl- egia with hyperkalium, polarizing cardioplegia with sodium channel inhibitor tetrodotoxin(TTX) could alleviate intracellular Na+ and Ca2+ overloading in isolated cardiomyocytes of rat, avoid structural damage and prevent ischemia-reperfusion injury.