Relationships between environmental organochlorine contaminant residues, plasma corticosterone concentrations, and intermediary metabolic enzyme activities in Great Lakes herring gull embryos

Experiments were conducted to survey and detect differences in plasma corti costerone concentrations and intermediary metabolic enzyme activities in he rring gull (Larus argentatus) embryos environmentally exposed to organochlo rine contaminants in ovo. Unincubated fertile herring gull eggs were collec ted from an Atlantic coast control site and various Great Lakes sites in 19 97 and artificially incubated in the laboratory. Liver and/or kidney tissue s from approximately half of the late-stage embryos were analyzed for the a ctivities of various intermediary metabolic enzymes known to be regulated, at least in part, by corticosteroids. Basal plasma corticosterone concentra tions were determined for the remaining embryos. Yolk sacs were collected f rom each embryo and a subset was analyzed for organochlorine contaminants. Regression analysis of individual yolk sac organochlorine residue concentra tions, or 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs), with indi vidual basal plasma corticosterone concentrations indicated statistically s ignificant inverse relationships for polychlorinated dibenzo-p-dioxins/poly chlorinated dibenzofurans (PCDDs/PCDFs), total polychlorinated biphenyls (P CBs), non-ortho PCBs, and TEQs. Similarly, inverse relationships were obser ved for the activities of two intermediary metabolic enzymes (phosphoenolpy ruvate carboxykinase and malic enzyme) when regressed against PCDDs/PCDFs. Overall, these data suggest that current levels of organochlorine contamina tion may be affecting the hypothalamo-pituitary-adrenal axis and associated intermediary metabolic pathways in environmentally exposed herring gull em bryos in the Great Lakes.