Evaluation of estrogenic activity of parabens and their chlorinated derivatives by using the yeast two-hybrid assay and the enzyme-linked immunosorbent assay.
We assessed the estrogen agonist activities of 21 parabens and their chlorinated derivatives by using yeast two-hybrid assays incorporating either the human or medaka (Oryzias latipes) estrogen receptor alpha (hERalpha and medERalpha, respectively), and by using hERalpha competitive enzyme-linked immunosorbent assay (ER-ELISA). In the two-hybrid assay with hERalpha, five parabens and three chlorinated derivatives exhibited estrogenic activity, and their relative activity (17beta-estradiol [E2] = 1) ranged from 2.0 x 10(-5) to 2.0 x 10(-4), with the highest activity observed in i-butylparaben. In the medERalpha assay, six parabens and six chlorinated derivatives exhibited estrogenic activity and their relative activity ranged from 2.7 x 10(-5) to 3.5 x 10(-3), with the highest activity observed in benzylparaben, its monochlorinated derivative, i-butylparaben, and n-butylparaben. Although medERalpha demonstrated an activity to E2 that was three times lower than that demonstrated by hERalpha, medERalpha has a higher sensitivity to parabens than hERa (1.3-8.9 times). Five parabens and two chlorinated derivatives exhibited a binding affinity to ERa in the ER-ELISA; of the parabens, i-butylparaben exhibited the strongest binding affinity. The yeast two-hybrid assay and the ER-ELISA also revealed that many of the assayed chlorinated parabens were much weaker than the parent compound. In addition, the results mainly showed that parabens with a bulk substituent (e.g., i-butyl and benzyl groups) had a higher activity than those with a sterically small substituent. It is considered that derivatization masks the apparent estrogenic activity of parabens, but the resulting chlorinated compounds may represent a potential hazard and therefore other toxicity tests should be performed to determine the toxicity of the chlorinated derivatives.
Terasaki
Masanori
M
Institute for Environmental Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan. terasaki@u-shizuoka-ken.ac.jp
Kamata
Ryo
R
Shiraishi
Fujio
F
Makino
Masakazu
M
D000818:Animals; D002713:Chlorine / Q000737:chemistry*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D047628:Estrogen Receptor alpha / Q000187:drug effects; D004967:Estrogens / Q000819:agonists / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D009990:Oryzias; D010226:Parabens / Q000737:chemistry / Q000494:pharmacology*; D020798:Two-Hybrid System Techniques
D047628:Estrogen Receptor alpha; D004967:Estrogens; D010226:Parabens; D002713:Chlorine