AIMTo investigate the effects of polarizing cardioplegia solution with sodium channel inhibitor tetrodotoxin (TTX) on intracellular free Na+ concentration ([Na+]i) in isolated cardiomyocytes of rat.

METHODSVentricular myocytes with beating were isolated from adult rat hearts by enzymatic dissociation, randomly created in group base, group STH2 (contrast group of ischemia/reperfusion) and group TFX (treated group). Both Group STH2 and group TTX were arrested by St. Thomas No. 2 cardioplegia solution and TTX cardioplegia solution respectively, the arrest/re-beating cell model imitating MIRI being established, and imaged by laser scanning confocal microscopy (LSCM) for measuring [Na+]i of cardiomyocytes in different period. The morphology of cardiomyocytes was observed under the inverted microscope.

RESULTS[Na+]i of cardiomyocytes in both group TTX and group STH2 after re-beating was higher than that in group base (P < 0.01), and [Na+]i in group TTX was lower than that in group STH2 (P < 0.01). During arrest, the elevation of [Na+]i in group TTX was lower than that in group STH2. During arrest, the elevation of [Na+]i in group TTX was lower than that in group STH2. Morphologically, after re-beating, the ratio of active cardiomyocytes with normal form in group TTX was higher than that in group STH2 (P < 0.01).

CONCLUSIONContrast depolarized cardioplegia solution, TTX cardioplegia solution could alleviate ischemia reperfusion injury and intracellular Na+ overload of cardiomyocytes.