J. van der Kolk

Interactions of 2,2′,4,4′,5,5′-hexachlorobiphenyl and 2,3,7,8-tetrachlorodibenzo-p-dioxin in a subchronic feeding study in the rat☆

Abstract Female (SD) rats were fed diets containing 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) in various concentrations for three months. PCB 153 had no significant effect on the body weight gain when given alone or in combination with TCDD. The increases in relative liver weights were additive. For thymic atrophy no interactive effects became apparent. PCB 153 had no effect on the EROD induction by TCDD. PROD induction by PCB 153 was diminished in the presence of TCDD. The level of TCDD in the liver was decreased by PCB 153. Increasing TCDD dosage led to an increase in PCB 153 levels.

Interactive effects of 2,2′,4,4′,5,5′-hexachlorobiphenyl and 2,3,7,8-tetrachlorodibenzo-p-dioxin on thyroid hormone, vitamin A, and vitamin K metabolism in the rat

Abstract Groups of rats were fed diets containing various concentrations of 2,3,7,8,-tetrachlorodibenzo-p-dioxin (TCDD) or 2,2,′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) alone or in combination, for 13 weeks, with the aim to investigate possible interactive effects on hormonal and vitamin plasma and liver levels. Decreases were found in total (TT4) and free (FT4) thyroxin plasma levels for both compounds, which were additive after four weeks. After 13 weeks however, the effect on TT4 and FT4 was synergistic. In addition, an increase in plasma retinol, a decrease in liver retinol and a sharp decline in liver retinylpalmitate concentrations were found after TCDD or PCB 153 administration. Coadministration resulted in an antagonistic effect of TCDD on the decrease in liver retinylpalmitate levels due to PCB 153.