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

The relationship between the morphological changes and vitamin A conte nt during the development of acute toxicity induced by polychlorinated biphenyl (PCB) in mouse parotid glands was investigated. PCB was admi nistered intraperitoneally at a single dose of 2 mg/kg. Ultrastructura l studies revealed remarkable morphological changes in the rough endop lasmic 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 da y after PCB administration. Then the activity of NADPH-cytochrome c re ductase increased 4 days after PCB administration. Subsequently, the v itamin A content of the parotid glands significantly decreased at 7 da ys compared with the control. These sequential changes in enzyme activ ities implied that the decrease of vitamin A content in the parotid gl ands may be partly due to catabolism of vitamin A by increased activit ies of microsomal enzymes induced by PCB. In conclusion, it is suggest ed that PCB also induces drug metabolizing enzymes in the parotid glan d cells and that the acute toxicity of PCB on this tissue may occur, a t least partly, through the reduction of vitamin A not only by the sec ondary effect from liver impairment but also by the locally accelerate d catabolism of vitamin A in the mouse parotid gland.