The Role of δ 2 -Opioid Receptors in the Regulation of Tolerance of Isolated Cardiomyocytes to Hypoxia and Reoxygenation

Hypoxia (20 min) and reoxygenation (30 min) were simulated on isolated rat cardiomyocytes to evaluate the cytoprotective effect of selective δ 2 -opioid receptor agonist deltorphin II, opioid receptor antagonist naloxone methiodide, μ-opioid receptor antagonist CTAP, κ-opioid receptor antagonist nor-binaltorphimine, ε 1 -opioid receptor antagonist BNTX, and δ 2 -opioid receptors naltriben. Deltorphin II was administered 5 min before reoxygenation, antagonists were administered 10 min before reoxygenation. The cytoprotective effect of deltorphin II was assessed by the number of cardiomyocytes survived after hypoxia/reoxygenation, as well as by the lactate dehydrogenase content in the incubation medium. It has been established that the cytoprotective effect of deltorphin II occurs at a concentration of 64 nmol/liter and is associated with activation of δ 2 -opioid receptors.