Comparisons of the effects of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin on chemically impacted and nonimpacted subpopulations of Fundulus heteroclitus: II. metabolic considerations

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Abstract
A previous paper reported resistance to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) toxicity in a subpopulation of Fundulus heteroclitus inhabiting the chemically impacted estuary of Newark Bay, New Jersey, as compared to a chemically nonimpacted subpopulation of F. heteroclitus in Tuckerton, New Jersey. This paper reports the results of toxicokinetic and metabolic investigations. The rates of [3H]TCDD elimination following a single dermal treatment of [3H]TCDD were similar between the Newark and Tuckerton F. heteroclitus subpopulations, as were the capabilities to metabolize TCDD. The Newark F. heteroclitus subpopulation consistently exhibited elevated hepatic P4501A catalytic activity (two‐ to fivefold), as measured by ethoxyresorufin O‐deethylase (EROD), compared to the Tuckerton subpopulation. EROD activity in Newark F. heteroclitus could not be induced by dermally administered [3H]TCDD, ranging from 0.020 to 8.0 ng/g [3H]TCDD. The Tuckerton fish exhibited a linear increase in EROD activity at 96 h following dermal administration of [3H]TCDD, ranging from 0.80 to 8.0 ng/g [3H]TCDD. The maximum mean induction in the Tuckerton fish was 30‐fold greater than the Tuckerton vehicle control mean. These data indicate that the Newark fish were resistant to both the toxicity of TCDD and the ability of TCDD to induce P4501A activity, which may imply an alteration in the Ah receptor complex of Newark F. heteroclitus.