The physiological significance and the change of the neurosteroid-producing enzyme in the brain under stress conditions.

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Steroid 5alpha-reductase is the enzyme that converts a number of steroids with a C-4,5 double bond and C-3 ketone to 5alpha-reduced metabolites, and the type 1 of two isozymes is present in the brain. We investigated immunohistochemically the change of the enzyme expression and the cellular appearance of 5alpha-reductase-containing rat C6 glioma cells by culturing these cells in vitro in stress conditions, that is, the serum-free medium. The expression of 5alpha-reductase was located in the perinuclear region under the serum-supplemented medium, but distributed in the cytoplasmic region under the serum-free medium. The expression of both GFAP and CNPase was the same between the two culture conditions. The cellular form was spinde in the serum-supplemented medium, and became hypertrophic and multipolar in the serum-free medium. However, the expression of 5alpha-reductase mRNA was the same indifferent of the presence of serum. The immunohistochemical change of 5alpha-reductase expression was induced by the change of enzyme localization within the cells, but not by the enzyme quantity.In the adrenal gland, which is thought to be involved in the stress reactions, 5alpha-reductase was located in the fascicular to reticular layer of the gland and the staining intensity of the enzyme increased after the removal of gonads and decreased by the supplementation of testosterone or estradiol. The enzyme was shown to be located by light and electron microsopy in the cytoplasm of Schwann cells and satellite cells in the peripheral nervous system.