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ATRAZINE EFFECTS ON EARLY PREGNANCY AND IMPLANATION IN THE RAT
Citation:
Cummings, A M., B. E. Rhodes, AND R L. Cooper. ATRAZINE EFFECTS ON EARLY PREGNANCY AND IMPLANATION IN THE RAT. Presented at Society for the Study of Reproduction, Madison, WI, July 15-18, 2000.
Description:
Atrazine Effects on Early Pregnancy and Implantation in the Rat.
A.M. Cummings, B.E. Rhodes*, and R.L. Cooper*.
Reproductive Toxicology Division, NHEERL, USEPA, Research Triangle Park, NC
Atrazine (ATR), an herbicide, can induce mammary tumors in rats. ATR can also suppress luteinizing hormone (LH) and prolactin (Prl) surges and disrupt pregnancy maintenance in rats. We reasoned that an ATR-induced suppression of Prl during early rat pregnancy would impair corpus luteum (CL) maturation, reduce progesterone secretion, and disrupt implantation. In this study we examined the effect of ATR on implantation in four strains of rats: Holtzman (HLZ), Long Evans (LE), Sprague Dawley (SD), and Fischer 344 (F344). Two dosing times, 1400 hr (PM) and 0200 hr (AM), were chosen corresponding to periods preceding the diurnal and nocturnal Prl surges of early pregnancy. Groups of animals within each strain received ATR once daily (AM or PM) by gavage at 0, 50, 100, and 200 mg/kg/day on days 1-8 of pregnancy (GD 0 = sperm +). These doses correspond to those which altered the estrogen-induced Prl surge in ovx rats in previous work. At necropsy on GD9, the number of implantations, and serum LH, progesterone (P), and estradiol (E), levels were evaluated. The experimental design precluded the assessment of peak Prl levels. ATR produced a significant decrease in body weight at 200 mg/kg in all strains. HLZ, F344, and SD rats showed a decrease in implantations with no pattern with respect to dosage or time of dosing. HLZ rats, alone, showed a significant increase in resorptions and a decrease in serum P (200mg/kg; both times). In F344, HLZ, and LE rats, a significant reduction in serum LH was seen at 200 mg/kg (AM or PM). We conclude that ATR has only minor and inconsistent effects on implantation and very early pregnancy in rats at these doses. [This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.]