Coplanar PCB congeners increase uterine weight and frontal cortical dopamine in the developing rat: implications for developmental neurotoxicity.

We show that developmental exposure of the laboratory rat to the coplanar polychlorinated biphenyl (PCB) congener 3,4,3',4'-tetrachlorobiphenyl (TCB) and the structurally similar congener 3,4,5,3',4'-pentachlorobiphenyl (PtCB) elevates dopamine (DA) concentrations in the prefrontal cortex (PFC). To determine whether these coplanar congeners are estrogenic, and may thus contribute to the elevations in PFC DA, we measured uterine wet weight (UWW) in prepubertal rats exposed to TCB or PtCB. For comparison, additional animals were exposed to either the ortho-substituted congener 2,4,2',4'-tetrachlorobiphenyl (o-TCB) or 3,4,5,3',4',5'-hexachlorobiphenyl (HCB), a coplanar congener highly resistant to metabolism. Both TCB and PtCB increased UWW, but this effect was blocked after exposure to the anti-estrogen ICI 182,780. Neither o-TCB nor HCB altered UWW. These results demonstrate that certain coplanar PCB congeners and/or their metabolites, are estrogenic, and suggest that exposure during critical periods of neuronal development may increase central DA concentrations, and by inference, alter behavior.