Dual Effects of Phytoestrogens Result in U-Shaped Doseresponse Curves

By Fernandez, Mariana F.

Book Id: WPLBN0000034656
Format Type: PDF eBook
File Size: 0.9 MB
Reproduction Date: 2005

Title:	Dual Effects of Phytoestrogens Result in U-Shaped Doseresponse Curves
Author:	Fernandez, Mariana F.
Volume:
Language:	English
Subject:	Government publications, United Nations., United Nations. Office for Disarmament Affairs
Collections:	Government Library Collection, Disarmament Documents
Historic Publication Date:
Publisher:	United Nations- Office for Disarmament Affairs (Unoda)


Citation APA MLA Chicago Fernandez, M. F. (n.d.). Dual Effects of Phytoestrogens Result in U-Shaped Doseresponse Curves. Retrieved from http://www.gutenberg.us/

Description
Government Reference Publication

Excerpt
Excerpt: Endocrine disruptors can affect the endocrine system without directly interacting with receptors, for example, by interfering with the synthesis or metabolism of steroid hormones. The aromatase that converts testosterone to 17(Beta)-estradiol is a possible target. In this paper we describe an assay that simultaneously detects aromatase inhibition and estrogenicity. The principle is similar to that of other MCF-7 estrogenicity assays, but with a fixed amount of testosterone added. The endogenous aromatase activity in MCF-7 cells converts some of the testosterone to 17(Beta)-estradiol, which is assayed by quantifying differences in the expression level of the estrogen-induced pS2 mRNA. Potential aromatase inhibitors can be identified by a dose-dependent reduction in the pS2 mRNA expression level after exposure to testosterone and the test compound. Using this assay, we have investigated several compounds, including synthetic chemicals and phytoestrogens, for aromatase inhibition. The phytoestrogens, except genistein, were aromatase inhibitors at low concentrations (< 1 micrometer) but estrogenic at higher concentrations (? 1 micrometer), resulting in U-shaped dose?response curves. None of the tested synthetic chemicals were aromatase inhibitors. The lowdose aromatase inhibition distinguished phytoestrogens from other estrogenic compounds and may partly explain reports about antiestrogenic properties of phytoestrogens. Aromatase inhibition may play an important role in the protective effects of phytoestrogens against breast cancer. Key words: aromatase inhibitors, endocrine disruptors, estrogenicity, phytoestrogens, U-shaped dose?response curves. Environ Health Perspect 110:743?748 (2002). [.