Inhibition of uroporphyrinogen decarboxylase by 3,3',4,4'-tetrachlorobiphenyl in chick embryo liver cell culture.

An assay was developed to measure uroporphyrinogen decarboxylase activity in 17-day-old chick embryo liver cells in culture. Decarboxylation products arising from the action of uroporphyrinogen decarboxylase upon uroporphyrinogen III were quantitated using high-pressure liquid chromatography. 3,3',4,4'-Tetrachlorobiphenyl (TCBP) was added to chick embryo liver cells and 24 h later the uroporphyrinogen decarboxylase activity in the cells was measured; a significant inhibition was found. On the other hand, when TCBP was added directly to the crude uroporphyrinogen decarboxylase enzyme no inhibition was noted. The inhibition of uroporphyrinogen decarboxylase observed in this study explains the accumulation of uroporphyrin and heptacarboxylic porphyrin in chick embryo liver cell cultures treated with TCBP.