Effects of acute 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure on plasma thyroid and sex steroid hormone concentrations and estrogen receptor levels in adult great blue herons

Adult great blue herons (Ardea herodias) were exposed intraperitoneally to a single dose of 20 mu g/kg body weight of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and sacrificed after 14 d. Approximately 1.9% of the total TCDD dose was measured in the liver. No differences were found in liver weight or liver to body weight ratio between control and TCDD-treated birds. Hepatic microsomal ethoxyresorufin O-deethylase (EROD) activity was induced sixfold above control activities in TCDD-exposed herons (p < 0.001). Plasma total T-4 concentration was significantly elevated in TCDD-exposed herons (p < 0.05). The TCDD treatment had no effect on plasma total T-4 levels, or on the plasma T-3 to T-4 ratio. No effect of this TCDD exposure was found on plasma 17 beta-estradiol or testosterone concentrations, or on hepatic estrogen receptor affinities and concentrations in male or female herons.