Distribution of glia maturation factor-like activity in organs and cells

Glia maturation factor (GMF) is a protein first isolated from the adult pig brain. GMF-like activity can be demonstrated in rat organs, including brain, kidney and heart. The activity in these organs is low in newborn animals, but increases with development, reaching the adult level in 1 or 2 weeks. GMF-like activities in the various organs are similar in physicochemical properties, being heat-labile, susceptible to proteolytic enzymes, and are associated with an acidic molecule of large size. Cultured rat glioblasts and C6 glioma cells, but not their conditioned media, contain large amounts of endogenous GMF-like activity. GMF obtained from brains and cultured glial cells also possess mitogenic action. Subcellular fractionation localizes GMF-like activity in the cytosol and in microsomal and nerve ending fractions. GMF-like activity is also detectable in bovine, sheep, monkey and human brains. The results suggest that GMF is ubiquitous in distribution, and at least a portion of it may be associated with the structural components of the cells.