DIRECT DETECTION OF OXYGEN FREE RADICAL GENERATION DURING INUTERO HYPOXIA IN THE FETAL GUINEA PIG BRAIN. ▴ 364

Abstract

Previous studies have shown that hypoxia is associated with lipid peroxidation in the brain of guinea pig fetuses. The present study tests the hypothesis that the hypoxia-induced increase lipid peroxidation is related to increase of oxygen free radical generation. Free radical generation was documented by measuring the signal of spin adducts using electron spin resonance spectroscopy (ESR). Fourteen pregnant guinea pigs of 16 days gestation (term=63 days) were divided into normoxic (n=7) and hypoxic (n=7) groups and exposed to 21% or 7% oxygen for 60 min., respectively. Fetal brain hypoxia was documented biochemically by decreased levels of ATP and phosphocreatine. Following anesthesia, fetal cerebral cortical tissue was excised and homogenized in a N2 bubbled ice-cold 100 mMα-phenyl-N-tert-butylnitrone (PBN) to trap oxygen free radicals generated in brain tissue. Trapped PBN spin adducts were extracted in toluene and ESR measurements were performed at -20°C. Peak height of the spin adduct signal spectrum was used as an index of the intensity of free radical formation and expressed as units/g dry tissues. Cortical tissue from hypoxic fetuses showed a significant increase in spin adducts (normoxic: 33.8±9.3 units/g tissue vs. hypoxic: 57.9±9.2 units/g tissue, 71% increase. p<0.01). The results demonstrate an increased production of oxygen free radicals in the guinea pig fetal brain during hypoxia, suggesting that hypoxia-induced oxidation of cell components, such as cell membrane lipids, proteins, (enzymes and receptors) and nucleic acids follows increased generation of oxygen free radicals, therefore it is a primary mechanism of hypoxic cellular dysfunction. (This study was supported by NIH HD-20337; MOD#94-135 and UCP#R-506-93;WUH).