Androgenic and Antiandrogenic Effects of Alkylphenols and Parabens Assessed Using the Reporter Gene Assay with Stably Transfected CHO-K1 Cells (AR-EcoScreen System)

An androgen receptor (AR)-reporter gene assay for some chemicals was examined using two different types of stably transfected CHO-K1 cell lines (AR-EcoScreen cells for androgenic activity and c-luc cells for cell toxicity evaluation). One stably expresses luciferase with androgen induction. The other stably expresses it without the need for androgen induction. We studied the responsiveness of the luciferase of AR-EcoScreen to androgen agonists and androgen antagonists. The luciferase activity of AR-EcoScreen was highly induced by androgens such as 5a-dihydroxytestosterone and testosterone. Furthermore, the luciferase activity of AR-EcoScreen was very susceptible to androgen antagonists such as hydroxyflutamide and cyproproterone acetate compared with that of MDA-kb2, which stably expresses androgen and glucocorticoid-responsive luciferase and represents a tool for screening for androgenicity. We examined the AR-reporter gene assay of some chemicals containing alkylphenols and parabens using AR-EcoScreen and c-luc cells (AR-EcoScreen system). None of the tested chemicals had any androgenic activity. However, 4-t-octylphenol, 4-n-dodecylphenol, 4-n-nonylphenol, 4-n-hexylphenol, 4-n-pentylphenol, 4-n-octylphenol, and 4-n-propylphenol exerted antiandrogenicity. Isobutylparaben, n-butylparaben, isopropylparaben, and n-propylparaben also had antiandrogenic activity. The level at which these parabens effects were observed is a value that is lower than the upper limit of the acceptable daily intake (ADI, 10 mg/kg/day). 4-Ethylphenol, 4-methylphenol, ethylparaben, and methylparaben had no effect on the androgen-responsive luciferase activity. We propose that the AR-EcoScreen system is suitable for a battery of titer-1 tests to identify chemicals that affect the endocrine system, and that the ADI value of total parabens may have to be lowered in Japan.