You are here:
Triclosan Exposure enhances the Uterotrophic Response to Low Doses of Ethinyl Estradiol (EE) in the Female Wistar Rat
Citation:
Louis, G., D. Best, AND T. E. STOKER. Triclosan Exposure enhances the Uterotrophic Response to Low Doses of Ethinyl Estradiol (EE) in the Female Wistar Rat. Presented at Endocrine Society meeting, Boston, MA, June 04 - 07, 2011.
Impact/Purpose:
TCS has also been reported to alter endocrine function by decreasing thyroxine and testosterone in rats; thus, raising new concerns that this antimicrobial may adversely affect human health.
Description:
Triclosan [TCS; (5-cbloro-2-(2, 4-dichlorophenoxy) phenol)] is an antimicrobial agent commonly found in personal care and sanitizing products, such as soaps, toothpaste and hair products. Recent studies have identified TCS in human breast milk, blood and urine. TCS has also been reported to alter endocrine function by decreasing thyroxine and testosterone in rats; thus, raising new concerns that this antimicrobial may adversely affect human health. Previously, we reported that oral exposure to TCS (150 mg/kg) advanced the age of vaginal opening and increased uterine weight, indicative of an estrogenic effect. In the weanling rat, TCS alone had no effect on uterine weight, whereas a combined exposure to EE (3 ug/kg) and TCS (4.69 mg/kg and greater) potentiated the effect of EE on uterine growth (i.e., uterine weight and epithelial cell height). To further characterize the combined action of TCS and EE, we examined uterine growth in the immature rat following EE treatment at concentrations that are more representative of phannaceutical doses (0.125 to 3 ug/kg). EE at concentrations as low as 0.25 ug/kg significantly increased uterine weight compared to vehicle alone, whereas EE at 0.125 ug/kg had no effect. We found that 9.375 and 18.75 mg/kg of TCS in combination with EE (0.25 ug/kg and higher) resulted in approximately a 25% increase in uterine weight compared to the uterine weights ofthose exposed to EE alone. In addition, the lowest dose of TCS tested (4.69 mg/kg) increased uterine weight greater than that observed in the weanlings exposed to EE alone only at the higher doses of EE (2 and 3 ug/kg). Thus, TCS enhances the uterine response to concentrations of EE that are lower than previously shown. The significance of these observations lies in the fact that the potentiation of EE by TCS was observed at doses of EE comparable to those used for birth control and post-menopausal management. Because the doses of TCS used were greater than exposures in humans, the implications for human health remain to be determined. The mechanism(s) through which TCS enhances EE activity is under examination. This abstract does not necessarily reflect EPA po/icy