PROBLEM: Injections of estradiol-17β (E2) are known to both induce anovulation and alter lymphocyte maturation in female mice. The current study examined whether the two events are related.
METHOD OF STUDY: Female (C3H/HeJ × 129J)F1 (C31) mice were injected with 20 μg of E2 from 0–3 days, or from 3–6 days, postpartum. At 8, 12, 20, 32, or 40 weeks of age, the animals were killed, T lymphocytes were characterized, and ovaries were histologically examined for the presence of corpora lutea.
RESULTS: Animals injected with E2 from 0–3 days postpartum had percentages of CD8+ thymocytes and CD8+ splenocytes that were always lower than in noninjected females, and the E2-injected animals never ovulated, even by 40 weeks of age. In contrast, animals injected with E2 from 3–6 days of age had percentages of CD8+ thymocytes and CD8+ splenocytes that, although initially lower than in control females, attained control values by 32 weeks of age. In addition, at 32 weeks of age a number of the 3–6-day E2-injected females ovulated, whereas at earlier ages none had. Further, injections of E2 had little effect on the percentages of CD4+ thymocytes and splenocytes in these animals.
CONCLUSIONS: The results suggest that E2-induced anovulation in C31 female mice is correlated with decreased levels of CD8+ lymphocytes, and an increased CD4+/CD8+ lymphocyte ratio.