ULTRASTRUCTURAL, BIOCHEMICAL, AND IMMUNOLOGICAL CHARACTERIZATION OF MALLORY BODIES IN LIVERS OF GRISEOFULVIN-TREATED MICE - FIMBRIATED RODS OF FILAMENTS CONTAINING PREKERATIN-LIKE POLYPEPTIDES

Abstract

Mallory bodies (MB) induced in hepatocytes by long term feeding of mice with griseofulvin were isolated, purified and examined by EM in ultrathin sections and negatively stained preparations. The major structural component of the MB was randomly oriented, unbranched rods of filaments; these were 175-250 nm long, 14-20 nm thick and covered by a dense fimbriate coat of laterally projecting 1.5-3 nm thick threads. Such lateral threads could extend for more than 20 nm and seemed to be involved in the interconnection of adjacent filaments and their association and aggregation into MB. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified filament material showed 6 major polypeptide bands with apparent MW ranging from 48,000-66,000. When the portion of the MB filament material that was soluble in solutions containing 8 M urea was allowed to reaggregate upon removal of the urea, an enrichment of 1 polypeptide component (.apprx. MW, 64,000) was seen. When frozen sections of liver tissue MB were subjected to indirect immunofluorescence microscopy they were specifically revealed by guinea pig antibodies directed against purified bovine prekeratin. No significant accumulation of MB was seen with a series of other antisera including those containing antibodies against tubulin, actin and vimentin, the major protein of the intermediate sized filaments predominant in mesenchymal cells. Apparently MB in livers of griseofulvin-treated mice and probably of human alcoholic hepatitis contain large amounts of prekeratin-like polypeptides assembled into a special form of fimbriated rods of 14-20 nm filaments. These filaments are morphologically different from other forms of intermediate sized and thick filaments, including the prekeratin-containing 6-11 nm tonofilament-like filaments present in various epithelial cells.