17β-Estradiol is critical for the preovulatory induction of prostaglandin E(2) synthesis in mice.

Aromatase-deficient (ArKO) mice are totally anovulatory due to insufficient estrogen production. However, sequential administrations of high doses of 17β-estradiol (E2) and gonadotropins were found to induce ovulation in these mice. Here, we examined how the ovulatory stimulation for ArKO mice alters the expressions of genes related to prostaglandin (PG) E(2) metabolism and ovarian contents of PGE(2), as PGE(2) is one of the critical mediators of ovulatory induction. The ovulatory stimulation significantly increased mRNA expressions of prostaglandin-endoperoxide synthase 2, PGE(2) receptor type 4 and sulfotransferase family 1E, member 1, in preovulatory ArKO ovaries. In contrast, it suppressed the mRNA expression of 15-hydroxyprostaglandin dehydrogenase. Furthermore, significant elevation in the PGE(2) contents was detected in the preovulatory ovaries of ArKO mice after stimulation with E2 plus ovulatory doses of gonadotropins. Thus, these analyses demonstrate a requirement of E2 for the preovulatory enhancement of PGE(2) synthesis, leading to future success in ovulation.