SUPEROXIDE-DISMUTASE DOES PROTECT THE CULTURED RAT CARDIAC MYOCYTES AGAINST HYPOXIA REOXYGENATION INJURY/

The effect of superoxide dismutase (SOD) on membrane integrity and flu idity of the cultured neonatal rat cardiac myocytes in vitro was inves tigated under the condition of hypoxia and hypoxia/reoxygenation. Lact ate dehydrogenase (LDH) concentration was used as the biochemical indi cator for the loss of cell membrane integrity. Fluorescence polarizati on (FP), average microviscosity (<(eta)over bar>) and anisotropy (Ast) , which are inversely proportional to the fluidity of cell membrane, w ere assayed. Cells were respectively exposed to hypoxia or hypoxia/reo xygenation for different periods of time in the absence or presence of SOD at various concentrations. Hypoxia alone or hypoxia/ reoxygenatio n brought injury to the cultured myocytes. This was demonstrated by ch anges in LDH and membrane fluidity. In the former LDH concentration gr adually increased in a time-dependent manner and the values of FP, <(e ta)over bar> and Ast were significantly increased. The changes in memb rane integrity and fluidity induced by hypoxia or hypoxia/reoxygenatio n could be prevented by adding SOD to the culture medium. The results provide a direct evidence that SOD (740 u.ml(-1), the effective dose) was effective in protecting cultured myocytes against the injury as we ll as an indirect evidence of free radical generation. Based on the re sults obtained from this study and the establishment of concept of opt imally effective dose by Bernier and Omar et al, it was suggested that some previous reports, in which no evidence was found both in protect ive effect of SOD and in free radical generation by using only one dos e in hypoxia/reoxygenation model, should be interpreted with caution.