The in vitro metabolism of 17-hydroxyprogesterone by ovaries of the goldfish, Carassius auratus, is affected by substrate concentration.
Ovaries of mature goldfish (Carassius auratus) were incubated with 17-[3H]hydroxyprogesterone and 0, 0.01, 0.1, 1, 10, and 100 micrograms/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 micrograms/ml 17P. 7 alpha-Tetrols were the major products (36-52%) with 0-1 microgram/ml substrate, but at 10 and 100 micrograms/ml 17,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha P) 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 5 alpha-reduced-7 alpha-hydroxylated metabolites are formed by enzymes of high activity but low capacity and serve to limit secretion of 17,20 alpha P and its 20 beta epimer to the period of maximum GtH stimulation.
Kime
D E
DE
Department of Animal and Plant Sciences, University of Sheffield, United Kingdom.
Abdullah
M A
MA
D019326:17-alpha-Hydroxyprogesterone; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D006054:Goldfish / Q000378:metabolism*; D006908:Hydroxyprogesterones / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D010053:Ovary / Q000201:enzymology / Q000378:metabolism*
D006908:Hydroxyprogesterones; D019326:17-alpha-Hydroxyprogesterone