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Kala Natarajan,¹ James W. Overstreet,¹ Jane M. Rogers,² Michael S. Denison,² Jiangang Chen,¹ Peter N. Lohstroh,¹ Daniel S. McConnell,³ and Bill L. Lasley¹

¹Center for Health and the Environment and ²Department of Environmental Toxicology, University of California, Davis, California, USA; ³University of Michigan, Ann Arbor, Michigan, USA

Abstract

In this article we report a simple and efficient method for detecting nonsteroidal estrogens in a biologic sample. This method uses polyclonal antibodies to estradiol (E₂) to immunoprecipitate these major biologically active steroidal estrogens, leaving behind the nonsteroidal estrogens, which are then detected in a cell-based transcriptional activation bioassay for estrogen receptor agonist. The immunoprecipitation method effeciently removed 99% of radiolabeled E₂ and estrone (E₁) from human serum. In experiments in which supraphysiologic concentrations of E₂ and E₁ to human serum, all of the immunoreactive estrogens were still removed by the immunoprecipitation protocol. We carried out an in vivo validation study of this method in which we treated female macaques with the xenoestrogen nonylphenol (NP) , during the late follicular phase of the menstrual cycle. We used blood samples collected before and after treatment to evaluate and characterize endogenous and exogenous serum estrogens. An immunoassay for E₂ did not detect the NP in treated monkeys. The cell-based bioassay also did not detect the estrogenic activity of NP because of its saturation by the endogenous serum steroidal estrogens. However, when steroidal estrogens were removed by immunoprecipitation, we detected the estrogenic activity of NP in the bioassay. Thus, this approach is appropriate for detecting exogenous, nonsteroidal estrogens in serum samples. Key words: cell bioassay, endocrine disruptors, nonylphenol, steroidal estrogens, xenoestrogens. Environ Health Perspect 110:791-795 (2002) . [Online 17 June 2002]

http://ehpnet1.niehs.nih.gov/docs/2002/110p791-795natarajan/ abstract.html

Address correspondence to B.L. Lasley, Center for Health and the Environment, University of California, Davis, One Shields Avenue, Davis, CA 95616-8615 USA. Telephone: (530) 752-8506. Fax: (530) 752-5300. E-mail: bllasley@ucdavis.edu

We thank L. Laughlin for her assistance at the California Regional Primate Research Center.

This work was supported by grants U01 AG121554, ES04699, and ES06198 from the National Institutes of Health.

Received 5 June 2001 ; accepted 7 February 2002.