Metabolism of progesterone in mouse brain

Incubation of whole mouse brain homogenate with [ 3H]progesterone resulted in two metabolites: the 5α-reduced product, 5α-pregnane-3,20-dione and another metabolite at a 3-fold greater yield. This differed from rat brain, which produced predominantly the 5α-reduced metabolite under the same conditions. Subcellular fractionation of mouse brain demonstrated a particulate location for the 5α-reduction of progesterone and a cytosolic location for the production of the unknown major metabolite. Treatment of this unknown metabolite with chromium trioxide resulted in a reconversion to progesterone, indicating the presence of a hydroxyl at position 3 or 20. Comparison of the chromatographic behaviour of the unknown metabolite with that of authentic progesterone derivatives suggested that this metabolite corresponds to 20-hydroxy-4-pregnene-3-one.