Hepatic Enzyme Induction and Acute Endocrine Effects of 2,3,3',4',6-Pentachlorobiphenyl in Prepubertal Female Rats

Abstract

Polychlorinated biphenyls (PCBs) with the labile 2,3,6-substitution are important components of atmospheric and certain food chain exposures, but little is known about their biological activities. Chlorobiphenyl 110 (2,3,3',4',6-pentaCB) was investigated in weanling female rats dosed ip on days 21 and 22 and killed on day 23 of age. The initial preparation of CB 110 markedly induced 7-ethoxyresorufin O-dealkylase (EROD) activity and was found to be contaminated with coplanar 3,3',4,4',5-pentaCB (CB 126). The contaminated preparation (CB 110C) was purified with activated charcoal (CB 110P). The CB 110P induced pentoxyresorufin O-dealkylase (PROD), was weakly uterotropic and a modest depleter of serum thyroxine (T4). CB 110C caused increased liver weight, induced EROD, PROD, and UDP glucuronyl transferase activities and caused a greater depletion of serum T4; on the other hand, it suppressed the PROD induction and the uterotropic effect of CB 110P. Hepatic residues of CB 110 were a constant 2-3% of the dose while those of CB 126 (from CB 110C) increased with increasing dose to as much as 50% of the dose.

Forms and Prevalence of Intersexuality and Effects of Environmental Contaminants on Sexuality in Cricket Frogs (Acris crepitans)

“…Various congeners and mixtures of PCBs, PCDFs, and PCDDs possess a spectrum of estrogenic, antiestrogenic, and antiandrogenic effects (27,(34)(35)(36)(37)(38). Soil, dust, and air near the contaminated sites contained both estrogenic and antiestrogenic PCBs and PCDFs, but antiestrogenicity dominates the net effect of the PCB/PCDF mixtures at these sites (28,36).…”

Polychlorinated biphenyl effects on avian hepatic enzyme induction and thyroid function

“…PCB 110 caused a significant decrease in circulating T 4 in rats with an ip injection of 32 mg/kg and had no effect on UDP-GT activity (Li et al, 1998). A mixture of PCB 110 contaminated with PCB 126 caused a significant decrease in circulating T 4 in rats with an ip injection of 32 mg/kg and induced UDP-GT activity with an ip injection of 4 mg/kg (Li et al, 1998). PCB 132 (ip injection of up to 96 mg/kg) in rats caused no significant changes in circulating T 4 , UDP-GT activity, TSH concentrations, or T 3 concentrations (Li et al, 2001).…”

“…These are all noncoplanar and therefore more likely less toxic than coplanar PCBs, but most environmental PCBs are non-coplanar congeners (Li et al, 2001). PCB 110 caused a significant decrease in circulating T 4 in rats with an ip injection of 32 mg/kg and had no effect on UDP-GT activity (Li et al, 1998). A mixture of PCB 110 contaminated with PCB 126 caused a significant decrease in circulating T 4 in rats with an ip injection of 32 mg/kg and induced UDP-GT activity with an ip injection of 4 mg/kg (Li et al, 1998).…”

Polychlorinated Biphenyl Congeners that Increase the Glucuronidation and Biliary Excretion of Thyroxine Are Distinct from the Congeners that Enhance the Serum Disappearance of Thyroxine

“…PCB-95 and PCB-99 (PB-type) had no effect on UGT activity toward T 4 . These results are supported by the observation that PCB-110 (a PB-type congener) did not induce hepatic UGT activity unless it was contaminated with PCB-126 (Li et al, 1998). When a PCB-contaminated soil sample is filtered with charcoal to remove the coplanar (TCDD-like) congeners, induction of UGT activity is abolished (Li and Hansen, 1997).…”