Estradiol protects clomiphene citrate-induced apoptosis in ovarian follicular cells and ovulated cumulus-oocyte complexes

Objective: To determine whether clomiphene citrate (CC) reduces E-2 level in the ovary and circulation and induces apoptosis in ovarian follicular cells and ovulated cumulus-oocyte complexes (COCs). If yes, to determine whether E-2 coadministration could protect against these adverse effects of CC. Design: A controlled prospective study. Setting: Laboratory research setting. Animal(s): Ninety sexually immature female rats that were 24-25 days of age. Intervention(s): The immature female rats were injected with a single dose of 10 IU of pregnant mare serum gonadotropin. After 48 hours, 10 IU of hCG along with 10 mg of CC per kilogram of body weight, with or without 2.0 mg of E-2 per kilogram of body weight were coadministered. After 16 hrs, the rats were killed; COCs were collected from oviduct and ovaries were isolated. Main Outcome Measure(s): Number of superovulated COCs, oocyte morphology, E-2 level in ovary and serum, histology of ovary, DNA fragmentation, and bax protein expression in ovary and COCs. Result(s): The number of COCs and E-2 level in ovary and serum were reduced, whereas membrane blebbing in oocytes, bax protein expression, and DNA fragmentation in ovarian follicular cells and ovulated COCs were induced after CC treatment. These adverse effects of CC were protected against if animals were coadministered with E-2. Conclusion(s): Clomiphene citrate-induced apoptosis in ovarian follicular cells (probably granulosa cells), thereby reducing E-2 level in ovary and circulation that might have resulted in poor development and maturation of oocytes leading to reduced ovulation.