Inhibitory effect of natural and environmental estrogens on thymic hormoneproduction in thymus epithelial cell culture

The present study was carried out to assess the direct effect of natural es trogen and environmental estrogens on thymus epithelial cell (TEC) producti on/secretion of the thymic hormone thymosin-alpha 1 by using the technique of quantitative high-performance liquid chromatography. The presence of est rogen receptors in the TECs was also investigated. Murine TECs were culture d in the experimental DMEM medium containing various concentrations of natu ral or environmental estrogens, which was followed by determining the produ ction of thymosin-alpha 1. The production of thymosin-alpha 1 by TECs was s ignificantly inhibited by increasing concentrations of 17 beta-estradiol (n atural estrogen) over 3 x 10(-11) M, genistein (phytoestrogen) over 3 x 10( -9) M, coumestrol (phytoestrogen) over 3 x 10-9 M, alpha-zearalanol (livest ock anabolic) over 3 x 10(-7) and bisphenol-A (plastic) over 3 x 10(-6) M. Small amounts of estrogen receptor were present in the TECs. The above resu lts clearly indicate that natural and environmental estrogens directly modu late TECs to produce thymic hormone probably through an estrogen receptor m echanism. Furthermore, our finding may be useful for evaluating biological effects of chemicals with estrogenic activity. (C) 1999 International Socie ty for Immunopharmacology. Published by Elsevier Science Ltd. All rights re served.