Sensitive immunoassays for human and rat GMFB and GMFG, tissue distribution and age-related changes

We developed sensitive and specific two-site enzyme immunoassays (EIA) for glia maturation factor beta (GMFB) and gamma (GMFG) using specific antibodies raised in rabbits. These assay systems enabled us to identify GMFB and GMFG (GMFs) in both human and rat samples and they were used to investigate the tissue distribution and serum concentrations of human and rat GMFs. In the case of rat, relatively high levels of GMFB were found in the central nervous system, except for the spinal cord, and in thymus and colon. Higher levels of GMFG were found in the thymus, spleen and colon. The distribution of GMFs in human was similar to that in rat. In the rat, the maximum serum concentration of GMFG was at 4 weeks of age. The decrease in its level was rapid for the first 30 days of life in both sexes. On the other hand, the concentration of GMFB in serum did not change significantly with age. Similarly, in human, the concentration of GMFG in serum was highest in the 21-30-year-old group and began to decrease rapidly in the 30-year-old group. In contrast, the concentration of GMFB did not change significantly during this period. No significant sex differences in the serum levels of GMFs were observed in human and rat. The present EIA systems are sufficiently sensitive for studying GMFs in human and rat organs.