Figure 1. Defective follicle maturation in Erβ^null ovaries.

Hematoxylin and Eosin stained sections of ovaries collected from gonadotropin-treated 4-wk-old wildtype rats show different stages of follicles including antral, and preovulatory or Graafian follicles (A-B). In contrast, the sections of ovaries collected from Erβ^null rats show numerous antral follicles of similar size (C-D).

Follicle counts were conducted to determine the numbers of antral and preovulatory follicle (Graafian follicle) in wildtype and in Erβ^null ovaries (E and G). Ovaries from wildtype rats contain antral and graafian follicles, but Erβ^null ovaries are devoid of preovulatory (Graafian) follicles (>600mm) and showing only numerous antral follicles (A-D, E and G). Erβ^null follicles do not undergo selection and dominance in response to gonadotropin and lack preovulatory maturation, which is observed in wildtype ovaries following stimulation with PMSG and hCG (F and H). hCG 4h, 4h after hCG administration to PMSG treated rats. Follicle count data represented as mean ± SEM. n ≥ 3. *P ≤ 0.05.