A time course investigation of vitamin A level and lipid composition of the liver endoplasmic reticulum in rats following treatment with congeneric polychlorobiphenyls.

The drug metabolizing enzyme activities, the vitamin A content and the fatty acid composition in the endoplasmic reticulum membrane were studied in rat liver after a single injection of the polychlorobiphenyls (PCBs) 3,3',4,4'-tetrachlorobiphenyl [(3,4)2Cl] or 2,2',4,4',5,5'-hexachloro-biphenyl [(2,4,5)2Cl], 300 mumol/kg each. The microsomal vitamin A level was markedly lowered 3 days after treatment with (3,4)2Cl, a coplanar type inducer of cytochrome P-450. A marked increase in microsomal AHH and UDPGT activities occurred within 3 days after injection of (3,4)2Cl whereas (2,4,5,)2Cl treatment enhanced APDM activity only. Arachidonic, stearic and linoleic acid microsomal contents were enhanced by the two congeners. (3,4)2Cl caused the proportion of docosahexaenoic acid to decrease. No highly significant correlation was found between the vitamin A content and lipid components in the microsomal membrane. However, the vitamin A level was inversely related to the activities of drug metabolizing enzymes induced by coplanar compounds (cytochrome P-450 towards benzo[a]pyrene and UDP glucuronosyl transferase towards 4-nitrophenol).