Age-Related Changes of Δ⁵-3β-Hydroxysteroid Dehydrogenase Activity in Mouse Oocytes

Abstract

Age-related changes of Δ⁵-3β-hydroxysteroid dehydrogenase (Δ⁵-3β-HSD) activity, using dehydroepiandrosterone as the substrate, were histochemically examined in the oocytes of 30-day-old, 60- to 90-day-old and 180- to 210-day-old mice. The activity was found in all the oocytes observed, and the percentage of the oocytes with a strong activity was significantly lower in 180-to 210-day-old mice than in 30-or60-to 90-day-old mice.In order to ascertain whether Δ⁵-3β-HSD activity in the oocytes of senescent animals is stimulated by gonadotrophins, as is inyoung animals, the activity in the oocytes of 180-to 210-day-old mice was detected after the oocytes were immersed in hCG-containing solutions. The percentage of the oocytes with a strong activity showed no significant differences between the percentage of the oocytes immersed in hCG-free solution. This result suggests that the oocytes of aged mice have lost sensitivity toward gonadotrophins.