CHANGES IN THE DEFENSE AGAINST FREE-RADICALS IN THE LIVER AND PLASMA OF THE DOG DURING HYPOXIA AND OR HALOTHANE ANESTHESIA/

Defenses against free radicals were evaluated in the dog under differe nt conditions of ventilation. Changes in the levels of reduced glutath ione (GSH), a-tocopherol (vitamin E), ascorbic acid (vitamin C) and th e lipid peroxidation end-products, estimated as malondialdehyde (MDA) and the activity of superoxide dismutase (SOD), were studied in serial liver biopsies from dogs ventilated with either oxygen, halothane and oxygen, hypoxic gas mixture of 8% oxygen and 92% nitrogen or halothan e under hypoxic conditions. Simultaneous determination of GSH, vitamin E and MDA were carried out in the plasma. The results showed time-dep endent depletion of GSH and vitamin E in liver and plasma and vitamin C in the liver. This was accompanied by a simultaneous increase in the levels of MDA. The magnitude of the change was in the following order : halothane and hypoxia > hypoxia > halothane and oxygen > oxygen. The greatest depletion was observed for vitamin E and the least for vitam in C. The rise in the level of MDA in plasma was much higher than in t he liver tissue. Hypoxia resulted in inhibition of liver SOD activity. It seems that increased production of free radicals under hypoxic con ditions may have overwhelmed the anti-oxidant defenses in the liver. I n addition, the much higher level of MDA in plasma, as compared to liv er tissue, may indicate that MDA could have originated in tissues or o rgans other than the liver and leaked into the blood, indicating possi ble damage in other locations in the body. (C) 1998 Elsevier Science I reland Ltd. All rights reserved.