Alterations in vitamin A metabolism by polyhalogenated aromatic hydrocarbons.

Adequate stores and adequate tissue levels of vitamin A are maintained by a balance of tissue demands and dietary intake of the vitamin and are modified by many factors, including xenobiotics. It is well established that exposure to polyhalogenated aromatic hydrocarbons (PHAH) decreases hepatic content of vitamin A. Recent findings indicate that hepatic depletion of vitamin A is accompanied by an increase in serum and renal vitamin A content and enhanced excretion of vitamin A metabolites in urine and feces. Examination of tissue retinoid profiles reveals that PHAH exposure causes the generation of increased amounts of polar retinoids. It is very likely that PHAH affect enzymes crucial for regulation of vitamin A storage as well as enhance activities of specific enzymes in vitamin A metabolic pathway.