Sulfation and uptake of the maturation-inducing steroid, 17α,20β-dihydroxy-4-pregnen-3-one by rainbow trout ovarian follicles |
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| Authors: | A P Scott Y Nagahama G Van Der Kraak J J Nagler |
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| Institution: | (1) Ministry of Agriculture Fisheries and Food, Directorate of Fisheries Research, Fisheries Laboratory, Lowestoft, Suffolk, NR33 0HT, United Kingdom;(2) Laboratory of Reproductive Biology, National Institute for Basic Biology, Okazaki, 444, Japan;(3) Department of Zoology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1;(4) Department of Fisheries and Oceans, Maurice-Lamontagne Institute, Mont-Joli, Quebec, Canada, G5H 3Z4 |
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| Abstract: | Rainbow trout ovarian follicles were incubated in vitro with tritiated 17 ,20 -dihydroxy-4-pregnen-3-one (17,20-P; maturation-inducing steroid). Within 18–24 h, 56–66% had been converted to tritiated 17,20-dihydroxy-4-pregnen-3-one 20-sulfate (identification confirmed by HPLC) and 27% had been taken up (absorbed) by the follicles. Addition of 125 ng of cold (non-tritiated) 17,20-P to the incubations caused a decrease in the percentage of 3H]-17,20-P which was sulfated (56%  10%) and an increase in the percentage that was taken up (27% 57%). Seven steroids were tested for their effectiveness in decreasing the sulfation and increasing the uptake of tritiated 3H]-17,20-P. The order of effectiveness was in both cases the same: 17,20-P > cortisol > 11-deoxycortisol > 17,20,21-trihydroxy-4-pregnen-3-one > 17-hydroxy-4-pregnene-3,20-dione > 17-estradiol > testosterone. This indicated that the processes of sulfation and uptake of 3H]-17,20-P were related to each other and led to the hypothesis that, when cold 17,20-P is added to the medium, it reduces the proportion of 3H]-17,20-P which is sulfated and thus allows more free 3H]-17,20-P to enter the ovarian follicles. This hypothesis was supported by the finding that each ovarian follicle had the capacity in vitro to sulfate only ca. 2 ng of 3H]-17,20-P per 18h but a capacity to take up > 500 ng per 18h.Gonadotropin I, Gonadotropin II, forskolin and phorbol-12-myristate-13-acetate (which all have an affect on steroid biosynthesis) did not affect the amount of 17,20-P which was sulfated. Sulfating activity was localized in the thecal cell layer of the follicle. The yolk fraction was shown to be responsible for absorbing the 3H]-17,20-P. |
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