Secretion of S-100 from rat C6 glioma cells.

Conditioned media from rat C6 glioma cells contain significant levels of S-100 immunoreactivity as determined by radioimmunoassay. The levels of extracellular S-100 detected could not be accounted for by the release of intracellular S-100 into the media from lysed cells. The extracellular form of S-100 exhibits fractionation properties and immunological characteristics that are different from those of the intracellular form of S-100 in C6 cells. While the intracellular S-100 levels increase as a function of days in culture, the extracellular S-100 levels are high until the cells reach confluency and are lower in postconfluent cultures. Altogether, our data suggest that C6 glioma cells secrete S-100, and that the quantitative levels of the intracellular and secreted forms of S-100 are differentially regulated.