ENHANCEMENT OF ALTERED HEPATIC FOCI DEVELOPMENT BY 2,3,7,8-TETRACHLORODIBENZO-PARA-DIOXIN (TCDD) - EFFECTS OF VITAMIN-A SUPPLEMENTATION AND THE TYPE OF DIET

In this study we investigated the modification of TCDD-induced enhancement of nitrosamine-initiated altered hepatic foci (AHF) development by dietary vitamin A supplementation and the type of diet. Vitamin A deficiency was shown to potentiate the effect of TCDD. Furthermore, severe vitamin A deficiency alone enhanced the development of AHF. A differential effect on AHF-development by the two types of diet used (purified vs cereal diet) was apparent. However, it was concluded that TCDD-induced depletion of hepatic stores of vitamin A is not a primary mechanism in liver tumour promotion induced by this compound. However, it may well be that TCDD-induced vitamin A deficiency acts as a tumour promoting stimulus in concert with an, as yet, unidentified mechanism of tumour promotion by TCDD. © 1990.