Hydroxyl radical formation in the perilymph of asphyxic guinea pig

To elucidate the role of hydroxyl radical ((OH)-O-.) species in the generation mechanism of the cochlear pathology induced by transient asphyxia and subsequent re-ventilation, the concentrations of 2,3-hydroxybenzoic acid (DHBA) and 2,5-DHBA, major products arising from the attack of (OH)-O-. upon salicylate, were measured in the perilymph of the guinea pig by the high performance liquid chromatography-electrochemical/UV method. The mean value of 2,3-DHBA concentration in the perilymph significantly increased from the pre-asphyxic level (6.4 mu M) to 7.6 mu M and 8.8 mu M during asphyxia of 3 min duration and at 5 min after the onset of re-ventilation, respectively. The 2,5-DHBA concentration was 7.9 mu M before asphyxia, and also significantly increased to 11.5 mu M and 16.2 mu M during and after asphyxia, respectively. These results strongly indicated that (OH)-O-. was generated in the perilymph of the asphyxic and re-ventilated guinea pig cochlea, and the significance of this increased (OH)-O-. in generating anoxia and re-perfusion injury is discussed with respect to iron and oxygen-derived free radicals. (C) 2000 Elsevier Science B.V. All rights reserved.