Chlorinated Aromatic Hydrocarbon Induced Modifications of the Hepatic Endoplasmic Reticulum: Concentric Membrane Arrays*

A number of commercial compounds having chlorinated aromatic hydrocarbon structures are used extensively for medical(3), industrial(4) and agricultural(5) purposes. Quantities of certain parent chlorinated aromatic hydrocarbons and metabolites have been repeatedly detected as residues in the food supply and tissues of birds, fish, and mammals(6-9) including man(10). Chlor-inated diphenyl-p-dioxins have been identified as contaminants of many commercial products, such as certain edible fats, herbicides and disinfectants. > It is suggested that the compound results from the conjugation of commercial chlorinated phenols(1l). Polychlorinated polyphenyls are among the most abundant chlorinated hydrocarbon global pollutants. Their contamination of the environment is a result of the widespread commercial use of these compounds for their properties of insulation, adhesiveness, thermoplasticity, chemical inertness, and insolubility. Following this investigation of sequential biochemical and ultrastructural alterations within the liver produced by three chlorinated aromatic hydrocarbons-chlorinated diphenyl-p-dioxin, polychlorinated biphenyls (PCBs), and a highly chlorinated triphenyl (PCT)-certain similarities of biochemical and ultrastructural effects of the compounds were observed. The livers of rats fed the chlorinated aromatic hydrocarbons consistently contained numerous multi-layered concentric membrane arrays, proliferated smooth * Portions of this paper were previously reported (1, 2). endoplasmic reticulum (ER), and altered micro-somal enzyme activity. Separate groups of male Sprague-Dawley rats initially weighing 100 grams were fed diets containing the following chlorinated aromatic hydrocarbons: 1% PCTs (Aroclor 5460), 0.02% PCBs (Aroclor 1254), and 0.002% chlorinated diphenyl-p-dioxin, respectively. At regular intervals the rats were deprived of food for 24 hours and sacrificed by exsanguination. The livers were weighed and portions were removed for electron microscopy. This tissue was immediately placed in veronal acetate buffered osmium tetroxide and cut into small cubes. Following one and one half hours of fixation, the tissues were dehydrated in a graded series of ethanol, cleared in propylene oxide and embedded in an Epon-Araldite mixture. Sections were cut at a thickness of 0.5-0.8 microns for light microscopic evaluation, and thinner sections at a thickness of approximately 60 millimicrons were cut and stained with uranyl acetate for electron microscopic examination. The remaining portions of the livers were perfused through the portal vein with isotonic KCl, weighed, and homogenized at 00 with two volumes of the salt solution. Microsomes were isolated from the post mitochondrial supernatant obtained by centrifugation at 9,000 X G for 20 minutes, washed by homogenization with KCl and re-centrifuged, resuspended in KCl equal to three volumes of the original liver material, and immediately assayed for the …