258 MECHANISM OFMICROVESICULAR STEATOSIS INDUCED BY PIRPROFEN: II~iIBITIOI OF NITO- CHONDRIAL ~-OXIDATION OF FATTY ACIDS BY THIS NOR-STEROIDAL ANTI-I~TORY DRUG

J. Gen~ve~ G. Labbe~ C. De~ott*, P. Lett~ron, E. Fr~neaux~ T. Le Din~ D. Larrey~ B. Hayat-Bonan~ D. Pessayre. INSERM U 24, and *Laboratoire Central d'Anatomie et de Cytologie Pathologiques, HSpital Beaujon, 92118 Clichy, France

Administration of pirprofen (Rangasil ®, Rengasil e) may produce microvesicular steatosis of the liver in humans. A similar lesion is observed after ingestion of valproic acid or hypoglycin, and is due to inhibition of mitochondrial E-oxidation. We determined the effects of pirprofen on mitochondrial B-oxidation.

In vitro, addition of pirprofen, 0.5, I or 2 mM, inhibited by 40%, 50%, and 53%, respectively, the formation of ketone bodies during incubation of palmitic acid with mouse liver mitochondria and the various cofactors necessary for B-oxidation. Inhibition was found to be reversible. In vivo, administration of pirprofen, 0.5~ i, or 2 mol.kg -I, inhibited by 35%, 50%, an-d 7--~?~, respectively the exhalation of [I~c]c02 during the first 6 hours following the administration of [14C]palmitic acid. Administration of pirprofen (2 mol.kg-l), i hr before the measurement, decreased by 36% plasma aceto-acetate, by 60% plasma B-hydroxy-butyrate, and decreased by 40% blood glucose. Administration of pirprofen (2 ~ol.kg-l), 6 hr before sacrifice, doubled hepatic triglycerides and led to microvesicular steatosis of the liver.

We conclude that pirprofen inhibits the mitochondrial B-oxidation of fatty acids in mice, probably explaining the microvesicular steatosis observed in humans.

259 ROLE OF LIVER MEMBRANE AUTOANTIBODIES IN AUTOIMMUNE HEPATITIS

G.Gerken,M.Manns,G. Ramadori,T. Poralla,H.P. Dienes~,K.-H. Meyer zum BUschenfelde I.Medizinische Kl inik und Pol ik l in ik and Xpathologisches Ins t i tu t der Johannes Gutenberg-Universit~t Mainz, Langenbeckstr. I, D-6500 Mainz, FRG

Four subgroups of autoimmune chronic active hepatitis (CAH-AI) can be defined by dif ferent autoantibodies (Lancet, 1:292, 1987). The aim of our study was to evaluate the pathogenetic, diagnostic and c l in ica l relevance of autoantibodies binding to the hepatocyte membrane (LMA). METHODS: Rabbit hepatocytes were isolated mechanically and classical LMA-assay was performed (NEJM, 294:578,1976). In addition, hepatocytes were isolated enzymatically (Liver, 3:358, 1983). V iab i l i t y of the cells was tested by trypan blue exclusion. Indirect immunofluorescence (IF) and immunoelectronmicroscopy (IELMI) was performed. Murine monoclonal antibody against organ-specific membrane-expressed determinant of LSP (2D3) served as control. Sera from patients with HBsAg-negative CAH (n=75), HBsAg-positive CAH (n=55), PBC (n=35), alcohol- and drug-induced l i ver diseases (n=50), non-hepatic autoimmune disorders (n=25) and healthy blood donors (n=20) were included in this study. RESULTS: Classical LMA-assay was positive in 56% of CAH-AI, which could not be differentiated into heterogeneous subgroups using this assay. When enzymatically isolated, viable hepatocytes were used, no l i ver membrane binding was observed in CAH-AI sera using IF and IELMI. In contrast, monoclonal antibody 2D3 showed a l inear membrane staining exclusively on viable hepatocytes. DISCUSSION: The classical LMA-assay is a valuable diagnostic marker for CAH-AI. I t does not help to distinguish the dif ferent subgroups of CAH-AI. Lack of membrane binding on viable hepatocytes indicates that LMA are directed against submembraneous constituents of the cel l , i .e. cytoskeletal components. A pathogenetic role of these "LMA" seems questionable. I t remains to be elucidated whether the disease process mediates membrane expression of primarily cytoplasmic antigens, i .e. under the influence of local ly produced lymphokines.

S135