[SIGNIFICANCE OF OPIOID RECEPTORS IN THE CYTOPROTECTIVE ACTION OF CHRONIC HYPOXIA DURING ANOXIA-REOXYGENATION OF...

It was investigated the role of δ-, μ- и κ-opioid receptors (ORs) in the development of cytoprotective effect of chronic normobaric hypoxia (CNH) using anoxia/reoxygenation of isolated cardiomyocytes. Adaptation to CNH was achieved by the maintenance of rats for 21 days at atmosphere containing 12% O2. Anoxia/reoxygenation of isolated cardiomyocytes of intact rats evoked a death of 23% cells and enhancement of lactate dehydrogenase (LDH) release from cells. Anoxia/reoxygenation of isolated cardiomyocytes of adapting rats induced a death of only 2.5% cells and LDH release decreased by 25%. Preliminary incubation of cells with the OR blocker naloxone (300 nM) or the δ-OR antagonist TIPP(ψ) (30 nM) or the selective δ2-OR antagonist naltriben (1 nM) or the μ-OR antagonist CTAP (100 nM) 25 min prior to anoxia abolished adaptive enhancement of cell survival and a decrease in LDH release. The blocking of δ1-OR by BNTX (1 nM) or κ-OR by nor-binaltorphimine (3 nM) not affected on the cytoprotection at CNH. Consequently, cardiac cell δ2- and μ-opioid receptors are involved in the cytoprotective effect of chronic normobaric hypoxia.