Influence of serum-free culture conditions on subcellular localization of steroid 5α-reductase in rat C 6 glioma cells

Abstract

Rat C 6 glioma cells are considered to be well characterized, and therefore commonly used as a model system to investigate the function of glial cells. However, recent study has shown that an alteration in the expression of their phenotypic antigens is observed when the cells are maintained under the serum-free conditions, proposing the possibility that various properties of glioma cells can be altered by the growth conditions. To test this possibility, the effects of serum-free culture conditions on the expression of steroid 5α-reductase (5α-R) type 1 isozyme in glioma cells were examined using immunocytochemical technique. Immunoreactivity of 5α-R type 1 was confined to the perinuclear region of glioma cells cultured in serum-containing medium, and observed in the cytoplasmic space as well as the perinuclear region of the cells cultured in serum-free medium. In contrast, serum deprivation failed to affect the expression of phenotypic antigens, glial fibrillary acidic protein (GFAP) and 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase). Further studies showed that the expression of cytoplasmic 5α-R immunoreactivity induced by serum deprivation was reversible, and might be attributed to removal of serum proteins rather than biologically active small molecules from culture medium. This alteration in the expression of 5α-R immunoreactivity is therefore considered to reflect the translocation of the enzyme from the perinuclear region to the cell cytoplasm rather than the induction of cytoplasmic enzyme, and suggest that the culture conditions cause an alteration in the subcellular localization of 5α-R type 1 isozyme without phenotypic change of the glioma cell.