MELATONIN RECOVERS ISCHEMIC TOLERANCE AND DECREASES THE SENSITIVITY OF MITOCHONDRIAL PERMEABILITY TRANSITION PORE OPENING IN HE HEART OF AGING RATS

: The effect of the hormone of pineal gland melatonin on the ischemic tolerance and the sensitivity of mitochondrial permeability transition pore opening in old rat heart were studied. It has been shown in the Langendorf's isolated rat heart that heart contractile functional changes under ischemia and reperfusion were more pronounced in old (24-27 months) rat hearts in comparison with the adult (5-6 months) animals. A two-week's in vivo course of intraperitoneal injection of melatonin (1,5 mg/kg weight) to old rats contributed to the rehabilitation of the functional changes of isolated heart after ischemia during reperfusion and decreased the sensitivity of mitochondrial permeability transition pore opening to Ca2+ and phenilarsinoxide in comparison with old animals which did not received melatonin. It was accompanied by the significant decreasing in mRNA bax expression in old rat heart, lessening in content of the superoxide radicals and dien conjugates and twice increasing in the activity of constitutive NO-synthase in heart mitochondria of old rat after a course of melatonin injection. The protective feffect of melatonin on the mitochondrial permeability transition pore opening could be used for correction of the cardiac dysfunction with aging.