PARENT SESSION

5B a - RA/ Ranking and Chemical Specific
Poster Hall
8:30 AM - Tuesday, 29 April 2003
Chair: Loonen, H.¹, ¹
Co-chair: McCarty, L.², ²

(TUP/213) Sorption of Estrogens and Estrogenic Compounds into Synthetic Membrane Vesicles and Their Relative Risk Estimation.

Yamamoto, Hiroshi¹, Morohoshi, Kaori¹, Shiraishi, Fujio¹, Morita, Masatoshi¹, Liljestrand, Howard², ¹ National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan² University of Texas at Austin, Austin, Texas, USA

ABSTRACT- Three estrogens, 17-ethynylestradiol (EE2), estrone (E1), and estriol (E3), and five estrogenic compounds, p-nonylphenol (NP), p-tert-octylphenol (OP), bisphenol-A (BPA), butylbenzylphthalate (BBP), and dibutylphthalate (DBP), were selected to assess their relative risk compared with 17-estradiol (E2). Membrane affinity of these compounds was evaluated using the synthetic membrane vesicle (liposome)-water system. Relative sorption coefficient (RSC) (i.e., RSC of E2 was assumed as 100) of selected compounds into liposome prepared from palmitoyl-oleoyl phosphatidylcholine (POPC), which is one of the most abundant species in biological membrane, was higher than 5,000 for NP and OP. While E3 had significantly lower RSC of 1.5, RSC values of the other compounds ranged from 136 to 773. Relative receptor binding affinity (RBA) of the selected compounds to estrogen receptor was determined using the ELISA system (TOYOBO Co., ligand screening system - estrogen ). The relative risk was estimated by simply multiplying RSC and RBA. Among the selected compounds, EE2 was slightly higher than E2 and had the highest estimated relative risk, followed by E1. NP and OP had similar relative risk of slightly above 5% of E2. E3, DBP, and BBP had the estimated relative risk of less than 2% of E2. As far as the reproductive risk of the effluent of wastewater treatment plant or the other aquatic environment for human and wild animals is concerned, the serious concern among the selected compounds should be over EE2 and E2. NP should also be considered as the serious concern due to the significantly higher concentration possibly detected in the environment (i.e., as high as 1000 ng/L) compared with the four estrogens, which are detected as high as 1 ng/L.

Key words: membrane affinity, estrogenic compounds, ralative risk, estrogen receptor assay