EFFECTS OF CHRONIC TREATMENT WITH SEVERAL HALOGENATED BIPHENYL ISOMERS ON THYROID AND ADRENAL HORMONE SECRETION
This investigation was undertaken to assess the consequences of chronic ingestion of several halogenated biphenyl mixtures with variable chlorine content and isomeric composition on rat thyroid and adrenal physiological parameters. Chronic ingestion of the PCB Aroclor 1016, 1242 and 1254 and the PBB hexabromobiphenyl and octabromobiphenyl induced reductions of circulating thyroid hormones. The PCB or PBB containing the highest halogenation and the highest concentration of highly halogenated isomers within the mixture proved to be most toxic. However, the chlorinated compounds were more toxic than the brominated compounds. A series of experiments were designed to address the question of whether the responsiveness of the thyroid gland to thyroid stimulating hormone (TSH) was altered following chronic exposure to Aroclor 1254 or hexabromobiphenyl. The ability of the thyroid gland of rats chronically exposed to Aroclor 1254 or hexabromobiphenyl to secrete T(,3) or T(,4) in response to TSH stimulation was significantly depressed from controls in a direct dose dependent manner. The magnitude of T(,4) suppression by either PCB or PBB was greater than that of T(,3). The effects of chronically ingested halogenated biphenyls, PCB, 1016, 1242 and 1254 and PBB hexabromobiphenyl and octabromobiphenyl on serum 17-keto steroids of adrenal origin were assessed. The biphenyl mixtures induced reductions in serum dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DS) which were correlated with the total percentage of halogenation and the isomeric composition of the molecule. The higher halogenated biphenyls with the exception of octabromobiphenyl exerted the greatest dimunitive influence on circulating DHEA and DS concentrations. Comparing the toxicity of the chlorinated with the brominated compounds suggests that the reductive influence against DHEA and DS was not a function of the chemical reactivity of the biphenyl substituents but was correlated with the degree of biphenyl substitution. Several PCB metabolites were found to significantly cross react with highly specific antisera for T(,3) and DHEA/DS. There was no evidence of a binding capacity of any PCB, PBB or metabolite against the T(,4) antisera. However, circulating levels of these compounds are most probably well below assay sensitivity.
Anatomy & physiology|Animals
CARBONE, JOHN PETER, "EFFECTS OF CHRONIC TREATMENT WITH SEVERAL HALOGENATED BIPHENYL ISOMERS ON THYROID AND ADRENAL HORMONE SECRETION" (1982). ETD Collection for Fordham University. AAI8219232.