Changes in the Activities of Hydroxysteroid Dehydrogenases in Rabbit and Hamster Oocytes during Meiotic Maturation

The activities of hydroxysteroid dehydrogenases (HSDs) were histochemically demonstrated in rabbit and hamster oocytes in the process of maturation, and the changes in steroid metabolism during meiotic maturation were examined. In rabbits, the percentages of oocytes showing the activities of Δ5-3β-HSD (with DHEA as the substrate), 17β-HSD (testosterone) and 20β-HSD (20β-hydroxyprogesterone) were always high and did not change during maturation, whereas those showing the activities of Δ5-3β-HSD (pregnenolone and 17α-hydroxy-pregnenolone), 17 β-HSD (estradiol-17β), 20α-HSD (20 α-hydroxyprogesterone) and 20β-HSD (17α-hydroxyprogesterone) decreased as the time after the hCG injection was prolonged. On the other hand, the activities of Δ5-3β-HSD, 17 β-HSD, 20α-HSD and 20β-HSD with eight substrates were almost always observed in hamster oocytes from 0 to 13 hrs after the hCG injection. The present findings suggested that the metabolic abilities of 20β-hydroxyprogesterone and androgen are constantly present in rabbit oocytes in the process of maturation, whereas those of progesterone, 17α-hydroxyprogesterone, 17α, 20β-dihydroxyprogesterone, 20α-hydroxyprogesterone and estrogen decrease during maturation. And it was also confirmed in hamster oocytes that the metabolic abilities of progesterone, 17α-hydroxyprogesterone, 17α, 20β-dihydroxyprogesterone, 20α-hydroxyprogesterone, 20β-hydroxyprogesterone, estrogen and androgen are always present and do not vary with maturation.