Exposure to Bisphenol A Modulates Hormone Concentrations in Gammarus pseudolimnaeus.

Abstract

Bisphenol A (BPA) is a pervasive anthropogenic chemical used to construct polycarbonate plastics. Worldwide more than 2.2 million metric tons of BPA are produced each year and 100 tons is released into the atmosphere. Several studies have shown that unregulated disposal of products containing BPA has resulted in global environmental contamination, making BPA responsible for the majority of the estrogenic activity that leaches from landfills into the ecosystem. The effluents from sewage treatment plants introduce BPA into rivers and streams where gammarid amphipods are often the most prevalent invertebrates. Gammarus pseudolimnaeus can provide a powerful invertebrate model system to investigate the endocrine-disruptive capabilities of BPA. However, techniques to assay hormone concentrations in amphipods have not been well developed. This study was designed to (1) quantify estrogen concentrations in juveniles and in adult female amphipods; (2) determine testosterone concentrations in juveniles and in adult male amphipods; and (3) delineate the effects of BPA on estrogen and testosterone concentrations following exposure. Amphipods were collected from a local stream that has high water quality and categorized as juvenile or adult based on size. Adults were subsequently sexed based on external morphology. Animals were assigned to one of four treatment groups: control (0 ug/L BPA), 10 ug/L BPA, 50 ug/L BPA and 100 ug/L BPA. Animals were housed in groups of 5 (adults) or 10 (juveniles) in BPA-free containers, and BPA in solution was added to each experimental container every 3 days over a 9 day treatment period. At the conclusion of the trials, amphipods were sacrificed, homogenized with protosol, and frozen at -80°C. Tissue extracts from homogenized amphipod samples were analyzed for estrogen or testosterone concentrations via radioimmunoassay. Hormone concentrations were quantified for each reproductive class. BPA was found to modulate hormone concentrations across treatment levels. The results of this study begin to elucidate the effects of BPA on reproductive hormones in freshwater amphipods, a new model system. Information gleaned from this and future studies may have profound implications for invertebrates and vertebrates since amphipods are central to many aquatic food webs. (poster)