Long-term persistence of polychlorinated biphenyl congeners in blood and liver and elevation of liver aminopyrine demethylase activity after a single high dose of aroclor 1254 to mice

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Poorly metabolized polychlorinated biphenyl (PCB) congeners are bioaccumulated in the bodies of rodents and humans. Little is known about the continuing biological effects of these persistent chemicals. To determine whether a single high dose of a PCB mixture to mice would have long-term effects on liver enzymes, Aroclor 1254 was given at a single dose of 500 mg/kg to (C57BL/6 × DBA/2)F1 female mice. Paired controls received olive oil. Mice were killed at intervals of 0.5 to 55 weeks after treatment and liver assessed for aminopyrine demethylase activity. At selected time points, blood and homogenates of liver and of whole carcass were analyzed for content of PCBs by gas chromatography with electron capture detection. Hepatic aminopyrine demethylase activity was significantly elevated in Aroclor-treated mice, relative to controls, for 42 weeks after treatment. A three- to fourfold increase persisted for at least 14 weeks, with a convergence of treated and control values thereafter. Significant amounts of nine PCB congeners were detected in carcass, liver, and blood; total carcass PCB, estimated on the basis of these congeners, correlated significantly with liver aminopyrine demethylase elevation, and a similar trend was noted for liver. At 42 weeks after treatment, total PCB levels were 70 mg/kg for carcass, 2.4 mg/kg for liver and 0.28 mg/kg for blood. Congener profiles were similar in all three compartments, with the majority of the retained chemical being 2,3′,4,4′,5- and 2,3,3′,4,4′-pentachlorobiphenyl and 2,2′,4,4′,5,5′-and 2,2′,3,4,4′,5′-hexachlorobiphenyl. These results suggest that congeners bioaccumulated after a high PCB dose retain biological activity in the body for nearly a year after treatment.