[Effect of chronic morphine treatment on free radical state].

The state of an enzymatic component of the antioxidant system, intencity of lipid peroxidation (LPO) in the liver, nitric oxide level in blood plasma were investigated in rats subjected to chronic morphine intoxication. Male Wistar rats were treated with introperitoneal injections of 1% morphine hydrochloride twice a day. The daily dose of morphine was gradually increased trom 10 mg/kg (1-2 days) to 20 mg/kg (3-4 days), and up to 40 mg/kg starting at the fifth day. The first group of animals (n=8) received morphine injections for 14 and 21 days. Chronic morphine treatment was accompanied by marked inhibition of the peroxide-utilizing antioxidants in liver. This creates favourable conditions for H2O2 toxicity. Howewer, low level of thiobarbituric acid reactive products suggests involvement of some scavenger, which inhibits hydrogen-peroxide induced free radical processes. In vitro experiments suggests that morphine may be involved into reduction of H2O2 level, whereas administration of morphine to rats may also employ nitric oxide as the scavenger of reactive oxygen species.