Contribution of opioid receptors to the cytoprotective effect of the adaptation to chronic hypoxia at anoxia/reoxygenation of isolated cardiomyocytes

We examined the role of opioid receptors in the cardioprotective effect of chronic continuous normobaric hypoxia in the model of anoxia/reoxygenation of isolated cardiomyocytes. Adaptation to hypoxia was provided by placing the rats for 21 days in an atmosphere with low O2 content. In intact rats, anoxia/reoxygenation of cardiomyocytes caused death of 23% cells and increased lactate dehydrogenase release from cardiomyocytes. In adapted rats, anoxia/ reoxygenation of cardiomyocytes caused death of only 2.5% cells and the release of lactate dehydrogenase decreased by 25%. Preincubation of the cells with opioid receptor blocker naloxone (300 nM) for 25 min eliminated the adaptive decrease in cell survival and reduction in lactate dehydrogenase release. Hence, opioid receptors of the cardiomyocytes contribute to the cytoprotective effect of chronic normobaric hypoxia.