93. DIFFERENTIAL REGULATION OF SOD1 AND SOD2 IN RAT LIVER DURING ONTOGENY

Superoxidase dismutase (SOD) is the main scavenger of superoxidase radicals in the mammalian body. The liver contains high levels of two SOD enzymes; Cu-Zn (SOD1) localized in cytosol and Mn SOD (SOD2) localized in mitochondria. The aim of the present study was to investigate the levels of SOD1 and SOD2 during development using enzymatic and immunological methodologies. Monospecific antibodies were prepared in rabbit against purified rat SOD1 and SOD2 polypeptides. Homogenates of fresh rat livers obtained from newborn, young, and adult rats were assessed for levels of SOD1 and SOD2 activity. It was found that the levels of SOD1 activity increased greater than ten-fold after birth, reaching adult levels after weaning. In contrast, the SOD2 level increased only four-fold after birth and reached essentially adult levels at weaning. SOD1 and SOD2 in newborn and young rat livers were not different in their molecular weight or charge from adult liver. Immunoblot quantitation indicated that changes in activity during ontogeny levels reflected the number of SOD1 and SOD2 molecules. These results show that SOD1 and SOD2 are differentially and independently regulated during ontogeny. It may be suggested that cytosolic and mitochrondrial SOD may play different roles in superoxide scavaging during liver development.