Antifertility Effect of Methoxychlor in Female Rats: Dose- and Time-Dependent Blockade of Pregnancy

摘要

Long-term exposure to methoxychlor (MXC), an estrogenic pesticide, produces infertility in rats, and short-term exposure blocks the decidual cell response. To address the short-term effects of MXC on fertility, the differential effects of MXC dosage and timing of administration (relative to implantation) on several gestational parameters were investigated. When MXC was administered during early pregnancy (Days 1-8), dose-dependent decline in implantations and uterine weight was seen with no effect on ovarian weight or corpora lutea; MXC reduced serum progesterone at all doses. Preimplantation administration of MXC (Days 1-3 of pregnancy) produced a decline in implantations and uterine weight, while post-implantation dosing (Days 4-8 of pregnancy) increased resorptions to 100%, decreased uterine weight, and reduced serum progesterone without affecting the number of implantations, ovarian weight, or number of corpora lutea. The data show that short-term MXC dosing during early pregnancy produces a dose-related infertility. The blockade of pregnancy by the preimplantation administration of MXC may be mediated by a direct effect on preimplantation uterine development. The fetal resorption seen following post-implantation dosing is considered a manifestation of both reduced serum progesterone and the direct disruption of normal decidual development by MXC. (Copyright (c) 1989 Academic Press, Inc.)