20α-Hydroxysteroid dehydrogenase and reductive metabolism of progesterone in mammalian cell cultures

Abstract

4- 14C-Progesterone was incubated with monolayer cultures of the HTC cells (rat hepatoma tissue culture cells). Four major metabolites were isolated and identified as 5α-pregnane-3,20-dione, 20α-hydroxypregn-4-en-3-one, 20α-hydroxy-5α-pregnan-3-one and 5α-pregnane-3β,20α-diol. The result indicates that these cells possessed 20α- and 3β-hydroxysteroid dehydrogenases and Δ 4-5α-reductase. The 20α-hydroxysteroid dehydrogenase activity was preponderant among the three. The HTC cells cultured with and without progesterone were subsequently homogenized and incubated with 4- 14C-progesterone in the presence of NADPH. The homogenates of the progesterone-induced cells exhibited higher 20α-hydroxysteroid dehydrogenase activity than the homogenates of the noninduced cells. Omission of the pyridine nucleotide cofactor decreased the enzyme activity, while addition of p-chloromercuribenzoate inhibited it. The 20α-hydroxysteroid dehydrogenase activity was retained in an ultracentrifuged supernatant fraction of the homogenates. In the same manner as above, 4- 14C-progesterone was incubated with monolayer cultures of three other established lines of mammalian cells; HeLa S 3 (human cervix carcinoma cells), Vero (green monkey kidney cells) and L 5 (mouse fibroblasts). The result demonstrated the presence of the 20α-hydroxysteroid dehydrogenase and Δ 4-5α-reductase more or less in all these lines of mammalian cells.