Publication Abstract

Sulfation and uptake of the maturation-inducing steroid, 17alpha, 20beta-dihydroxy-4-pregnen-3-one, by rainbow trout ovarian follicles

Sulfation and uptake of thematuration-inducing steroid, 17,20beta-dihydroxy-4-pregnen-3-one, by rainbow trout ovarianfollicles

A.P. Scott, Y. Nagahama G. Van Der Kraak and J.J. Nagler

Rainbow trout ovarian follicles were incubated in vitro withtritiated 17α,20β-dihydroxy-4-pregnen-3-one(17,20β-P;maturation-inducing steroid). Within 18-24 h, 56-66% had been converted to tritiated 17α,20βdihydroxy-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) 17,20β-P to the incubations caused a decrease in the percentage of [³H]-17,20β-P which was sulfated (56%-10%)and an increase in the percentage that was taken up (27%-57%). Seven steroids were testedfor their effectiveness in decreasing the sulfation and increasing the uptake of tritiated[³H]-17,20β-P. The order of effectiveness was in both cases the same: 17,20β-P > cortisol >11-deoxycortisol > 17α,20β,21-trihydroxy-4-pregnen-3-one > 17α-hydroxy-4pregnene-3,20-dione > 17β-estradiol > testosterone. This indicated that the processes ofsulfation and uptake of [³H]-17,20β-P were related to each other and led to the hypothesis that, whencold 17,20β-P isadded to the medium, it reduces the proportion of [³H]-17,20β-P which is sulfated and thusallows more free [³H]-17,20β-P to enter the ovarian follicles. This hypothesis was supported bythe finding that each ovarian follicle had the capacity in vitro to sulfate only ca. 2 ngof [³H]-17,20β-P per 18h but a capacity to take up > 500 ng per 18h.

Gonadotropin I, Gonadotropin II, forskolinand phorbol-12-myristate-13-acetate (which all have an affect on steroid biosynthesis) didnot affect the amount of 17,20β-P which was sulfated. Sulfating activity was localized in thethecal cell layer of the follicle. The yolk fraction was shown to be responsible forabsorbing the [³H]-17,20β-P.

Reference:

A.P. Scott, Y. Nagahama G. Van Der Kraak and J.J. Nagler, 1995. Sulfation and uptake ofthe maturation-inducing steroid, 17,20beta-dihydroxy-4-pregnen-3-one, by rainbow troutovarian follicles. Fish Physiology and Biochemistry, 14: 301-311.

A.P. Scott*, Y. Nagahama G. Van Der Kraak and J.J. Nagler

Fish Physiology and Biochemistry, 14: 301-311