EFFECT OF CORTISOL ON THE METABOLISM OF 17-HYDROXYPROGESTERONE BY ARCTIC CHARR AND RAINBOW-TROUT EMBRYOS

The effect of cortisol on the in vitro metabolism of [H-3]17(-)hydroxy progesterone ([H-3]17OHP) was studied during embryonic development of Arctic charr (Salvelinus alpinus) and rainbow trout (Oncorhynchus myki ss). In the absence of cortisol, rainbow trout embryos metabolized [H- 3]17OHP largely to androstenedione (A(4)) and androstenetrione (11-KA) with a minor conversion to 17,20 beta-dihydroxy-4-pregnen-3-one (17,2 0P). In the presence of cortisol, this biosynthesis was inhibited. On the other hand, cortisol had no apparent inhibitory effect on the natu re of metabolism of [H-3]17OHP by Arctic charr embryos. In these embry os [H-3]17OHP was metabolized mainly to 17,20P with a minor conversion to A(4) and without the formation of 11-KA that was seen in rainbow t rout. When incubated in the presence of [H-3]cortisol both Arctic char r and rainbow trout embryos produced 11 beta-hydroxyandrostenedione (1 1 beta-OHA) as the major metabolite, with a minor conversion to an unk nown steroid. The catabolism of the cortisol by salmonid embryos may r eflect the ability of the embryo to inactivate or detoxify cortisol to protect itself from the adverse effects of this biologically potent s teroid hormone The study indicates the existence of species-specific d ifferences in the nature of metabolism of [H-3]17OHP and the inhibitor y effect of cortisol on this metabolism.