IDENTIFICATION OF, AND DEVELOPMENT OF RADIOIMMUNOASSAYS FOR 17-ALPHA,21-DIHYDROXY-4-PREGNENE-3,20-DIONE AND 3-ALPHA,17-ALPHA,21-TRIHYDROXY-5-BETA-PREGNAN-20-ONE IN THE OVARIES OF MATURE PLAICE (PLEURONECTES-PLATESSA)

Ovaries from a female plaice (Pleuronectes platessa) that had been injected with human chorionic gonadotrophin were incubated in vitro with 17α-hydroxy[1,2,6,7-3H]progesterone. The major steroids produced by the ovaries were tentatively identified as 17α,21-dihydroxy-4-pregnene-3,20di-one (11-deoxycortisol; 17,21-P), 17α,21-dihydroxy-5β-pregnane-3,20-dione (3α,17,21-P-5β). A high proportion of these steroids was found in a conjugated form (sulphates or glucuronides). Radioimmunoassays were developed for 11-deoxycortisol and for 3α,17,21-P-5β and were applied to fractions of mature male and female plaice plasmas and plaice ovarian incubates that had been separated on thin-layer chromatography. The presence of all three steroids, in vivo and in vitro, was confirmed. Particularly high amounts of conjugated 3α,17,21-P-5β were found in the plasma of mature females (200-400 ng ml-1). The 3α,17,21-P-5β radioimmunoassay also identified 3α,17α-dihydroxy-5β-pregnane-20-dione in all three fluids, despite the fact that this steroid was not among the radioactive incubation products of the ovary. These findings are compared with those from another flatfish, the dab (Limanda limanda), where the major gonadal steroids have been shown to be 17α,20α-dihydroxy-4-pregnen-3-one and its 5β-pregnane (3-keto and 3β-hydroxyl) metabolites. © 1990.