Potential estrogenic activity of triclosan in the uterus of immature rats and rat pituitary GH3 cells

Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol; TCS) is used as an antimicrobial agent in personal care, pharmaceutical, industrial, and household products. In this study, we established an in vivo model for screening estrogenic activity of TCS in the uteri of immature rats. In addition, we employed temporarily transfected cells with plasmids containing estrogen response element (ERE) and progesterone (P4) response element (PRE) sequences. We found that uterine weight was significantly increased by 17α-ethinylestradiol (EE) as a positive control and TCS at doses of 7.5, 37.4, and 187.5 mg/kg. In addition, the expressions of calbindin-D(9k) (CaBP-9k) and complement C3 (C3) were significantly induced by EE and TCS in the uteri of immature rats, indicating that TCS can induce their expression mediated by estrogenic activity. Co-treatment with steroid antagonists ICI 182,780 (ICI) and RU 486 in conjunction with TCS (37.5 mg/kg) reversed TCS-induced uterine weight and CaBP-9k mRNA and protein expression increases in immature rats. Moreover, ERE and PRE luciferase activity was evaluated in GH3 cells following treatment with TCS. Concentrations of TCS at increasing doses (10⁻⁹, 10⁻⁷, and 10⁻⁵ M) resulted in a significant increase in ERE luciferase activity compared to control; however, no difference was observed in PRE luciferase activity following TCS treatment. To confirm that ER signaling is involved in TCS-induced CaBP-9k expression, we treated GH3 cells with the anti-estrogen ICI, which can block TCS-induced up-regulation of CaBP-9k in these cells. Taken together, these results indicate that TCS has an estrogen-like property, which may be mediated through an ER-involved signaling pathway in both in vivo and in vitro models.