Teratogenicity and immunotoxicity of 3,3′,4,4′,5-pentachlorobiphenyl in C57BL/6 mice

Administration of 3,3′,4,4′,5-pentachlorobiphenyl (pentaCB) to female C57BL/6 mice at doses from 130.5 to 522 μg/kg body weight resulted in the dose-dependent formation of fetal cleft palate and hydronephrosis. The estimated relative potency of 3,3′,4,4′,5-pentaCB compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was in the range of <0.07-0.04. The immunotoxicity of 3,3′4,4′,5-pentaCB and two structurally-related congeners, 3,3,′,4,4′-tetraCB and 3,3′4,4t́,5,5′-hexaCB, was investigated in male C57BL/6 mice by determining their suppression of the splenic plaque-forming cell response to sheep red blood cells. The potencies of these compounds relative to TCDD were determined from the ratios of their corresponding ED₅₀ values and were 0.77-0.55 (3,3′,4,4′,5-pentaCB), 1,1-0.29 (3,3′,4,4′,5,5′-hexaCB) and 0.14-0.03 (3,3′,4,4′-tetraCB). These results demonstrate that the immunosuppressive activities of the PCB congeners relative to TCDD were much higher than observed for many other TCDD-like responses in mice and other laboratory animals.