Quantification of cardioprotective gene expression in porcine short-term hibernating myocardium.

Several cardioprotective proteins are induced during myocardial ischemia, such as heat shock proteins and anti-apoptotic Bcl-2-related proteins which, when experimentally overexpressed, have been shown to prevent ischemia-induced myocyte loss. As this pathophysiological induction is obviously not sufficient to prevent losses of myocytes, we analysed whether it could occur under moderate myocardial ischemia with hibernation, thus potentially contributing to myocyte protection under these conditions. Therefore, using anesthetized pigs with documented myocardial hypoperfusion and short-term hibernation, we investigated the left ventricular mRNA expression of the inducible heat shock protein Hsp70 and of the anti-apoptotic Bcl-XL in comparison with the pro-apoptotic Bak and Fas expression. For transcriptional analyses, the porcine cDNA sequences of Bcl-XL, Bak and Fas were identified by polymerase chain reaction (PCR) or by screening of a porcine heart cDNA library and cloned. Using reverse transcription polymerase chain reaction (RT-PCR), we observed an unchanged mRNA expression of inducible Hsp70, Bcl-XL, Bak and Fas after 85 min of hypoperfusion in the short-term hibernating myocardium, as well as after 30 min of subsequent reperfusion in the stunned myocardium, compared with transcription in a non-hypoperfused control area of the same ventricle. In conclusion, the mRNA expression of inducible Hsp70 and of several apoptosis-modulating proteins is not altered during moderate myocardial ischemia resulting in short-term hibernation of the affected area and during subsequent stunning.