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 intraperitoneall y to a single dose of 20 mu g/kg body weight of 2,3,7,8-tetrachlorodib enzo-p-dioxin (TCDD) and sacrificed after 14 d. Approximately 1.9% of the total TCDD dose was measured in the liver. No differences were fou nd in liver weight or liver to body weight ratio between control and T CDD-treated birds. Hepatic microsomal ethoxyresorufin O-deethylase (ER OD) activity was induced sixfold above control activities in TCDD-expo sed herons (p < 0.001). Plasma total T-4 concentration was significant ly 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 rati o. No effect of this TCDD exposure was found on plasma 17 beta-estradi ol or testosterone concentrations, or on hepatic estrogen receptor aff inities and concentrations in male or female herons.