You are here:
EFFECTS OF AMITRAZ ON PREGNANCY MAINTENANCE AND DEVELOPMENT IN THE RAT
Citation:
Narotsky, M G., D S. Best, AND R L. Cooper. EFFECTS OF AMITRAZ ON PREGNANCY MAINTENANCE AND DEVELOPMENT IN THE RAT. Presented at Society for the Study of Reproduction, Vancouver, British Columbia, Canada, August 1-4, 2004.
Description:
EFFECTS OF AMITRAZ ON PREGNANCY MAINTENANCE AND DEVELOPMENT IN THE RAT. Michael G. Narotsky, Deborah S. Best, and Ralph L. Cooper. Reproductive Toxicology Division, NHEERL, ORD, US Environmental Protection Agency, Research Triangle Park, NC.
Amitraz, an insecticide and acaricide, has been shown to disrupt luteinizing hormone (LH) secretion in rats, most likely via a-noradrenergic antagonism in the hypothalamus. Here, we sought to determine the effects of amitraz on pregnancy maintenance when administered during the LH-dependent period of pregnancy (days 7-10). F344 rats were administered amitraz, in water, by gavage at 0, 10, 20, or 40 mg/kg/d on gestation days 6-10. The dams were allowed to deliver and litters were examined on postnatal days 1 and 6. Nongravid uteri were stained with 2% ammonium sulfide to confirm cases of full-litter resorption. Maternal toxicity was noted at 40 mg/kg, as evidenced by weight loss early in the dosing period and piloerection. Full-litter resorption was observed in one (8%) dam at 20 mg/kg and in six (55%) dams at 40 mg/kg; the latter incidence was significant. For dams with surviving litters, parturition was slightly, but significantly (p<0.01) delayed at 40 mg/kg; however, all gestation lengths were within normal limits and no adverse effects were associated with parturition. Although pup weights were comparable for all groups, prenatal loss was significantly increased in surviving litters at 40 mg/kg; the mean ? SE incidence per litter was 18.9 ? 6.9%, compared to 5.9 ? 3.2% for controls. Eye defects (microphthalmia, anophthalmia) were observed in a dose-related pattern in zero, one (8%), five (38%), and three (60%) litters of the respective dose groups; this incidence was significant at the highest dose. Thus, consistent with a disruption of LH secretion, amitraz caused pregnancy loss when administered during the LH-dependent period of gestation. The slight delay in parturition may also be related to amitraz-induced changes in hormonal profiles. However, the developmental effects (prenatal loss and eye defects) seen in surviving litters are likely due to unrelated modes of action. [This abstract does not necessarily reflect EPA policy.]