Substrate concentration affects the in vitro metabolism of 17-hydroxyprogesterone by ovaries of the carp,Cyprinus carpio |
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| Authors: | David E Kime Mohammad A S Abdullah Miroslawa Sokolowska-Mikolajczyk Piotr Epler |
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| Institution: | (1) Department of Animal and Plant Sciences, University of Sheffield, Sheffield, SIO 2UQ, United Kingdom;(2) Department of Ichthyobiology and Fisheries, Academy of Agriculture, Krakow-Mydlniki, Poland;(3) Present address: Mariculture and Fisheries Department, Kuwait Institute for Scientific Research, PO Box, 1638, Salmiya, Kuwait;(4) Dept Animal and Plant Sciences, University of Sheffield, PO Box 601, Sheffield, S10 2UQ, UK |
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| Abstract: | Carp ovarian tissue was incubated with 3H-17-hydroxyprogesterone in the presence of 0, 0.1, 1, 10, and 100 μg ml−1 unlabeled 17-hydroxyprogesterone. The pattern of metabolites formed showed a marked variation with substrate concentration.
Formation of glucuronide and sulphate conjugates was important only at low substrate concentration. At high substrate concentration
(10 and 100 μg ml−1) 17,20α-dihydroxy-4-pregnen-3-one was the major metabolite, but at intermediate concentrations polar 7α-hydroxypregnanetetrols
predominated. The results support the hypothesis that at low substrate concentrations conjugating, 5α-reducing and 7α-hydroxylating
enzymes, of high activity but low capacity, act as scavengers to deactivate any steroids formed during the relatively low
pituitary gonadotrophin secretions which are necessary for oocyte development, but that during the prespawning gonadotrophin
surge when high levels of substrate are present these enzymes are saturated and 17,20α-dihydroxy-4-pregnen-3-one (17,20αP)
becomes the major ovarian steroid. The possible role of 17,20αP during oocyte final maturation requires further examination. |
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| Keywords: | carp Cyprinus carpio ovary substrate concentration 17 20α -dihydroxy-4-pregnen-3-one steroid metabolism |
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