RESUMEN
The mechanisms underlying myocardial protection by sevoflurane post-conditioning are unclear. In the present study, we tested two hypotheses: (i) that sevoflurane post-conditioning produces cardioprotection via a phosphatidylinositol-3-kinase (PI3-K)-dependent pathway; and (ii) combining sevoflurane and ischaemic post-conditioning offers an additional benefit against reperfusion injury. Rat isolated perfused hearts were exposed to 25 min ischaemia followed by 90 min reperfusion. Sevoflurane post-conditioning was induced by administration of sevoflurane (3.0 vol%) for 15 min from the onset of reperfusion. In some groups, 15 micromol/L LY294002, a selective PI3-K inhibitor, was coadministrated with sevoflurane. Other groups of hearts were exposed to ischaemic post-conditioning or combined sevoflurane plus ischaemic post-conditioning in the presence and absence of LY294002. After 15 min reperfusion, phosphorylation of Akt and glycogen synthase kinase 3beta (GSK3beta) was determined by Western blot analysis. Infarct size was determined by 2,3,5-triphenyltetrazolium chloride staining and subsarcolemmal mitochondrial lesions were assessed by electron microscopy after 90 min reperfusion. Sevoflurane post-conditioning significantly decreased infarct size compared with control hearts (31 +/- 2 vs 42 +/- 3%, respectively; P < 0.05), diminished mitochondrial lesions and increased phosphorylation of Akt and GSK3beta, as did ischaemic post-conditioning. However, combined sevoflurane plus ischaemic post-conditioning did not further improve the cardioprotective effects compared with either intervention alone. Sevoflurane-mediated cardioprotection was abolished or inhibited by 15 micromol/L LY294002. In conclusion, sevoflurane acts during early reperfusion after ischaemia to salvage the myocardium by activating PI3-K. The combination of sevoflurane plus ischaemic post-conditioning does not offer any additional benefit over either intervention alone.