Synthesis of 20 alpha-hydroxylated steroids by ovaries of the dab (Limanda limanda).

Dab (Limanda limanda) ovarian fragments were incubated in vitro with either [4,7-3H]pregnenolone or 17 alpha-hydroxy[1,2,6,7-3H]progesterone to investigate the pattern of steroidogenesis. A major enzyme found in the dab ovary was 20 alpha-hydroxysteroid dehydrogenase. Among the steroids that were tentatively identified in ovarian incubates were 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P). 17 alpha,20 alpha-dihydroxy-5 beta-pregnan-3-one, 3 beta, 17 alpha,20 alpha-trihydroxy-5 beta-pregnane (3 beta,17,20 alpha-P-5 beta), and 3 alpha,17 alpha,20 alpha-trihydroxy-5 beta-pregnane. The presence of these steroids in plasma of mature female and male dabs was studied by radioimmunoassay. The antiserum was raised against 17,20 alpha-P. The 17,20 alpha-[3H]P label was produced by incubating place milt with 17 alpha-hydroxy [3H]progesterone. The radioimmunoassay was shown to have a high cross-reaction with the 5 beta-reduced analogues of 17,20 alpha-P and was therefore used, in conjunction with thin-layer chromatography, to measure the steroids. High concentrations of both 17,20 alpha-P and 3 beta,17,20 alpha-P-5 beta found in female and male dab plasma. The possible role of these steroids is discussed.