Toxicological Sciences 59, 291-296 (2001)
Copyright © 2001 by the Society of Toxicology
REPRODUCTIVE AND DEVELOPMENTAL TOXICOLOGY |
Mercury Vapor and Female Reproductive Toxicity
* National Institute of Environmental Sciences, MD A2-01, Research Triangle Park, North Carolina 27709;
ManTech Environmental Technology, Inc., Research Triangle Park, North Carolina 27709; and
Research Triangle Institute, Research Triangle Park, North Carolina 27709
Epidemiological studies finding menstrual cycle abnormalities among women occupationally exposed to Hg° prompted us to investigate the mechanisms of reproductive toxicity of Hg° in the female rat. Nose-only Hg° vapor inhalation exposures were conducted on regularly cycling rats 80–90 days of age in dose-response and acute time-course studies, which have previously proven useful as a model to identify ovarian toxicants. Vaginal smears were evaluated daily and serum hormone levels were correlated with cycle and with ovarian morphology at necropsy. Exposure concentration–related effects of Hg° were evaluated by exposing rats to 0, 1, 2, or 4 mg/m3 Hg° vapor 2 h/day for 11 consecutive days. Tissue Hg levels correlated with exposure concentration and duration. Exposure of rats to 4 mg/m3 (but not 1 or 2 mg/m3) Hg vapor for 11 days resulted in significant decreases in body weights relative to controls. Estrous cycles were slightly prolonged in the 2 and 4 mg/m3 dose groups, and serum estradiol and progesterone levels were significantly different in the 4 mg/m3 group compared to controls. The alterations in cycle and hormones at the 4 mg/m3 exposure concentration were attributed to body weight loss and generalized toxicity. In the time-course study, rats were exposed to 2 mg/m3 Hg° or air beginning in metestrus and evaluated daily for 8 days. A lengthening of the cycle was detected and morphological changes were observed in the corpora lutea (CL) after exposure for 6 days. To determine if changes in the CL and cyclicity correlated with a functional defect, rats were exposed to Hg° vapor and evaluated for pregnancy outcome. There were no significant effects on pregnancy rate or numbers of implantation sites when rats were exposed to 1 or 2 mg/m3 Hg° for 8 days prior to breeding, or when exposed for 8 days after breeding. These studies indicate that exposure to Hg° vapor altered estrous cyclicity, but had no significant effect on ovulation, implantation, or maintenance of first pregnancy during exposure of short duration in female rats.
Key Words: mercury vapor; menstrual cycle; female reproductive toxicity..
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