Early and differential decrease in natural retinoid levels in C57BL/Rij and DBA/2 mice by 3,4,3',4'-tetrachlorobiphenyl.

3,4,3',4'-Tetrachlorobiphenyl (TCB) administered by weekly ip injections of 1.5 to 100 mg kg-1 for 4 weeks induced a dose dependent decrease in retinoids in female C57BL/Rij and DBA/2 mice (5 to 7 weeks of age). However, the response differed between the two strains of mice. In C57BL/Rij mice, a dose dependent decrease in liver retinol (up to 60%), retinyl palmitate (up to 40%), and serum retinol (up to 80%) occurred, while in DBA/2 mice a decrease in serum retinol (up to 80%) only was observed. The effects of 3,4,3',4'-TCB on retinoid levels were more pronounced than on toxicity (e.g., decrease in thymus and body weight, increase in liver weight, and induction of AHH activity). This finding suggests that reduction in retinoid levels is a very sensitive parameter for the toxicity of polychlorinated biphenyls (PCBs). In addition, in these experiments the induction of aryl hydrocarbon hydroxylase (AHH) did not correlate with the decrease in retinoid levels in C57BL/Rij and DBA/2 mice, suggesting that the mixed function oxidase (MFO) system is not involved.