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The Effects of Simazine, a Chlorotriazine Herbicide, on Female Pubertal Development*
Citation:
Zorrilla, L., E. K. GIBSON, AND T. E. STOKER. The Effects of Simazine, a Chlorotriazine Herbicide, on Female Pubertal Development*. REPRODUCTIVE TOXICOLOGY. Elsevier Science Ltd, New York, NY, 29(4):393-400, (2010).
Impact/Purpose:
Here we report the effects of a 21 day exposure to simazine on pubertal development and estrous cyclicity in the female rat using the U.S. Environmental Protection Agency (EPA) Endocrine Disruptor Screening Program (EDSP) Female Pubertal (Tier 1) protocol.
Description:
Chlorotriazine herbicides, such as atrazine and its metabolites, have been shown to target the neuroendocrine regulation of male and female reproductive development. However, no studies have evaluated the effects of the chlorotriazine simazine on pubertal development in the female rat. Here we report the effects of a 21 day exposure to simazine on pubertal development and estrous cyclicity in the female rat using the U.S. Environmental Protection Agency (EPA) Endocrine Disruptor Screening Program (EDSP) Female Pubertal (Tier 1) protocol. The study was conducted in two blocks. In the first block, Wistar rats were exposed orally to 0, 12.5, 25, 50, or 100 mg/kg of Simazine from postnatal day (PND) 22 to 42. In the second block, rats were exposed from PND 22 until the first day of estrus after PND 62 to 0, 12.5, 25, 50, 100 and 200 mg/kg of simazine. In block 1, vaginal opening (VO) was delayed, the number of normal cycles was significantly decreased, and the day of first estrus was delayed compared to controls. In block 2, VO and the day of first estrus was delayed following the onset of VO, but the number of normal estrous cycles was not different than controls. In addition, both blocks showed a significant decrease in serum prolactin (PRL) concentrations following simazine exposure. This study clearly demonstrates that simazine delays the onset of puberty in the female rat and decreases serum PRL similar to other chlorotriazines. The extended dosing period after VO provides a sufficient time period to monitor the effects of a toxicant on estrous cyclicity, an important measure for reproductive competence.
