Both Aroclor 1254, a commercial polychlorinated biphenyl (PCB), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) elicit common aryl hydrocarbon (Ah) receptor-mediated effects including the induction of aryl hydrocarbon hydroxylase (AHH), a cytochrome P-450-dependent monooxygenase, the inhibition of the T-cell dependent plaque forming cells in response to sheep red blood cells (in C57BL/6 mice) and cleft palate in C57BL/6 mice. However based on ED50 values from dose-response studies with Aroclor 1254 and 2,3,7,8-TCDD, it was apparent that the latter compound is at least 105 times more potent. Cotreatment of rat hepatoma H-4-II E cells or C57BL/6 mice with an ED80-100 dose of 2,3,7,8-TCDD plus various sub-toxic (or effective) doses of Aroclor 1254 clearly shows that the commercial PCB can significantly antagonize 2,3,7,8-TCDD-mediated AHH induction (in vivo and in vitro), immunotoxicity and teratogenicity. In vitro Ah receptor binding studies suggests that Aroclor 1254 competitively inhibits the Ah receptor binding of 2,3,7,8-TCDD and this may account for the antagonist activity of the commercial PCB.
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Health, Toxicology and Mutagenesis