| Abstrakt: |
Ovaries of mature goldfish (Carassius auratus) were incubated with 17-[3H]hydroxyprogesterone and 0, 0.01, 0.1, 1, 10, and 100 µg/ml 17-hydroxyprogesterone (17P). The major products were quantified after separation by thin-layer and high-performance chromatography. The results show that substrate concentration markedly affects the pattern of metabolites. Glucuronides and sulfates decreased from 7.2 ± 2.0 and 28.5 ± 4.4% of recovered radioactivity, respectively, in the absence of added 17P to insignificant yields at 10 µg/ml 17P. 7α-Tetrols were the major products (36-52%) with 0-1 µg/ml substrate, but at 10 and 100 µg/ml 17,20α-dihydroxy-4-pregnen-3-one (17,20αP) was the major metabolite and there were low yields of other products. 11-Deoxycortisol was produced in significant amounts only at low substrate concentrations. The results support the hypothesis that 5α-reduced-7α-hydroxylated metabolites are formed by enzymes of high activity but low capacity and serve to limit secretion of 17,20αP and its 20β epimer to the period of maximum GtH stimulation. Copyright 1994, 1999 Academic Press |
