OBJECTIVETo investigate whether the cardioprotective effect of hemin against ischemia/reperfusion (I/R) injury is through the inhibition of calpain activity, and to explore its underlying mechanism.

METHODSSixty-four SD rats were randomly divided into eight groups (n = 8): sham, I/R, MDL+ I/R, MDL, hemin + I/R, hemin, and ZnPP + hemin+ I/R, ZnPP. Iangendorff isolated rat heart perfusion model was used. The rat hearts were suffered from 40 min of ischemia followed by 30 min of reperfusion. After that, left ventricular developed pressure (LVDP) was recorded. Infarct size and release of lactate dehydrogenase (LDH) were measured. Calpain, heme oxygenase (HO), and caspase 3 activities were evaluated. Expression of calpastatin protein was detected by Western blot.

RESULTS(1) After suffered from ischemia/reperfusion, the calpain activity and caspase 3 activity increased. MDL28170, an inhibitor of calpain, prevented ischemia/reperfusion induced increases in LDH and infarct size, improved the LVDP recovery. (2) Compared with ischema/reperfusion rat hearts, pretreatment of hemin enhanced the HO-1 activity, decreased the calpain and caspase 3 activities, declined LDH release and infarct size, and improved LVDP recovery. (3) Ischemia/reperfusion reduced the expression of calpastatin protein in rat hearts, which was inhibited by hemin pretreatment. And HO-1 inhibitor could abolish the cardioprotection of hemin.

CONCLUSIONCardioprotective effect of hemin against ischemia/reperfusion injury is through the inhibition of calpain activity, the mechanism might be involved in the increase in calpastatin protein expression.