AIM and METHODS: Rat myocardial mRNA was extracted and mitochondrial sarcomeric creatine kinase (sMiMi-CK) was used as labled probed in vitro myocardial ischemia/reperfusion rats. Northern blot was performed to determine the changes of sMiMi-CK mRNA in different periods of ischemia/reperfusion and the protective effect of phosphocreatine (PCr).RESULTS:During early ischemial (10 min) mRNA was decreased about 18 24%. After reperfusion mRNA decreased again. PCr effectively prevented the decrease of mRNA expression of sMiMi-CK. CONCLUSION:The results indicated that PCr may possess protective effect on anoxic and reoxygenated myocardium.