Abstract: Objective: To observe the influence of hypotaurine on ischemia/reperfusion injury(IRI) in isolated hearts in rats and to study its machanism.Methods: The ischemia/reperfusion(I/R) model of isolated perfused hearts was established by stopping and reperfusing Krebs-Henseleit(KH) fluid to the hearts of the rats.The changes of maximal rate of the pressure(+LVdp/dt_max) increase,maximal rate of the pressure(-LVdp/dt_max) decrease,left ventricular developed pressure(LVDP) of heart and heart rate(HR)were observed.Colorimetric method was used to assay the activity of lactate dehydrogenase(LDH),superoxide dismutase(SOD) and the content of malondialdehyde(MDA).Results: In the presence of 10^-6 or 10^-5 mol/L hypotaurine,±LVdp/dt_max was higher(P<0.05 or P<0.01),the leakage of mycardial LDH was attenuated(P<0.01),the SOD activity was increased(P<0.05 or P<0.01) and the content of MDA was decreased after reperfusion(P<0.01).Conclusions: Hypotaurine can prevent ischemia/reperfusion injury in isolated rat hearts,the mechanism of which may be related to its ability of clearing the oxygen-derived free radicals and stabilizing the cell membrane of the myocardium.