Liver Cell Estrogen Receptor Binding in Prespawning Female Largemouth Bass, Micropterus salmoides, Environmentally Exposed to Polychlorinated Biphenyls

Estrogen-receptor–like binding was partially characterized in liver tissue of prespawning female largemouth bass, Micropterus salmoides (LMB). Saturation and Scatchard analyses exhibited estrogen binding activity with high affinity (K_d in the 10⁻⁹ M range) and limited capacity (nuclear = 37.4 fmol/g tissue; cytosol = 234 fmol/g tissue). Androgens, progestins, and cortisol competed poorly for binding in competition studies. Thus, LMB liver estrogen binding activity possesses similar properties to estrogen receptors (ER) described in other vertebrates. In a study of prespawning female LMB from Lake Hartwell, SC/GA, a reservoir contaminated by polychlorinated biphenyls (PCBs), individuals environmentally exposed to high levels of PCBs had significantly lower ER binding capacity (Bmax) and higher nonspecific binding (NS) than fish from a relatively uncontaminated reference location. Fish obtained at a site with intermediate levels of PCBs did not exhibit the expected decrease in Bmax. The lower Bmax observed in fish from the location with high PCB contamination is consistent with the reported behavior of liver ER in fish experimentally exposed to PCBs. Increased NS in the ER assays could be related to elevations in albumin associated with the PCB exposure. Received: 15 July 1996/Revised: 17 September 1996