INDUCTION OF DRUG-METABOLIZING-ENZYMES BY POLYCHLORINATED BIPHENYL IN THE PAROTID-GLAND AND RELATION TO CHANGES IN VITAMIN-A CONTENT AND MORPHOLOGICAL-CHANGES

The relationship between the morphological changes and vitamin A content during the development of acute toxicity induced by polychlorinated biphenyl (PCB) in mouse parotid glands was investigated. PCB was administered intraperitoneally at a single dose of 2 mg/kg. Ultrastructural studies revealed remarkable morphological changes in the rough endoplasmic reticulum, nucleus, Golgi apparatus and the secretory granules at 7 days after the administration of PCB. The activities of adenosine monophosphatase (AMPase) and alkaline phosphatase were increased 1 day after PCB administration. Then the activity of NADPH-cytochrome c reductase increased 4 days after PCB administration. Subsequently, the vitamin A content of the parotid glands significantly decreased at 7 days compared with the control. These sequential changes in enzyme activities implied that the decrease of vitamin A content in the parotid glands may be partly due to catabolism of vitamin A by increased activities of microsomal enzymes induced by PCB. In conclusion, it is suggested that PCB also induces drug metabolizing enzymes in the parotid gland cells and that the acute toxicity of PCB on this tissue may occur, at least partly, through the reduction of vitamin A not only by the secondary effect from liver impairment but also by the locally accelerated catabolism of vitamin A in the mouse parotid gland.