2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN AFFECTS RETINOL ESTERIFICATION INRAT HEPATIC STELLATE CELLS AND KIDNEY

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a highly toxic environment al contaminant, interferes with retinoid homeostasis. To elucidate the underlying mechanism, the activities of lecithin:retinol and acyl-CoA :retinol acyltransferase (LRAT and ARAT) were determined in liver, kid ney, and hepatic parenchymal and nonparenchymal cell fractions from ra ts 7 days after a single oral dose of 10 mu g TCDD/kg body weight(b.w) . Severely depressed LRAT activity in hepatic stellate cells, and grea tly increased LRAT activity in kidneys, as well as decreased ARAT acti vity in stellate cells, were seen in TCDD-treated rats. Although the r elevance of decreased ARAT activity under physiological conditions is not clear, the changed LRAT activities most likely contributes signifi cantly to the TCDD-induced effects on tissue retinyl ester levels. It is intriguing that TCDD affects LRAT activity in hepatic stellate cell s and kidney in opposite directions. The results suggest that effects of TCDD on retinyl ester tissue levels could be due to a specific inte raction with retinoid metabolism.