The rat hepatocyte plasma membrane organic anion binding protein is immunologically related to the mitochondrial F1 adenosine triphosphatase beta-subunit.

A 55-kD organic anion binding protein (OABP) was identified previously in liver cell plasma membrane sinusoidal subfractions. Although this protein was localized to the surface of hepatocytes by immunofluorescence, immunoblot analysis revealed reactivity toward both plasma membrane and mitochondrial fractions. To clarify these findings, an immunoreactive clone from a rat liver cDNA expression library was isolated, the 1,500-base pair cDNA insert was sequenced, and the corresponding beta-galactosidase fusion protein was expressed and purified. The resulting sequence corresponded to that of the rat mitochondrial F1-adenosine triphosphatase (F1-ATPase) beta-subunit. This protein and OABP are of similar size and are mutually immunologically cross-reactive. That the antigen was present on the cell surface as well as in mitochondria was suggested from studies of immunoprecipitation after cell-surface iodination, and light- and electron-microscopic immunocytochemistry. Photoaffinity labeling of bovine F1-ATPase with high-specific-activity [35S]sulfobromophthalein revealed binding only to the beta-subunit. Hepatocyte uptake of bilirubin and sulfobromophthalein requires cellular ATP and mitochondria also transport these organic anions, which at high doses inhibit respiration. The presence of an organic anion binding site on the F1-ATPase beta-subunit suggests that it may play a role in these processes.

Carbohydrate-deficient transferrin, a marker for chronic alcohol consumption in different ethnic populations.

Serum levels of carbohydrate-deficient transferrin (CDT) were determined in a racially mixed population of 107 alcoholics, 18 healthy, nonalcoholic control subjects, 62 abstinent alcoholics, and in 64 Caucasian patients with various nonalcoholic liver diseases. The upper limit of normal CDT levels was 80 mg/liter (2 SD above the mean). CDT values exceeding this level were found in more than 80% of Black, Puerto Rican, and Caucasian alcoholics who had consumed greater than or equal to 50 g of alcohol/day for 1 month or longer prior to testing. Puerto Rican alcoholics had higher CDT values than the Black and Caucasian ethnic groups; however, these differences were significant only when compared to the Black population. Of 64 patients with nonalcoholic liver diseases, one individual with chronic active hepatitis (CAH) with an alcohol consumption of 20 g/day, and 10 of 26 subjects with primary biliary cirrhoses (PBC), who claimed to consume either no or only occasional moderate amounts of alcohol, had CDT levels ranging from 81 to 144 mg/liter. Seven of these individuals were in advanced stages of PBC. Total transferrin levels were variable and not significantly different in all subject groups studied. CDT/total transferrin ratios were increased in most patients with abnormal amounts of CDT, and there was a significant correlation between these ratios and CDT levels in all study groups. Serum enzyme parameters as well as red blood cell mean corpuscular volumes did not correlate with CDT values.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of alcoholism and liver disease in the appearance of serum antibodies against acetaldehyde adducts.

We recently presented preliminary data indicating the presence of antibodies against acetaldehyde adducts in sera of over 70% of alcoholic patients. To assess the respective roles of liver disease and alcohol consumption as well as the specificity of this immune response, 141 patients in various stages of alcoholic and nonalcoholic liver diseases were tested by a hemagglutination assay. Sixty-three (73%) of 86 alcoholics had antibody titers above control levels (p less than 0.0001). Alcohol consumption of these individuals was significantly higher (p less than 0.001) than that of those alcoholics with normal titers. Twenty-two patients (39%) with nonalcoholic liver diseases also had elevated levels of antibodies against acetaldehyde adducts (p less than 0.0005); of these, 8 had primary biliary cirrhosis (7 in Stages III and IV), 9 had chronic active hepatitis (6 with cirrhosis) and 5 had acute (virus- or drug-induced) hepatitis. Antibody titers did not correlate with levels of transaminase or alkaline phosphatase activity, nor with bilirubin, and albumin. However, in 52 alcoholics and in nonalcoholic patients with biopsy-confirmed liver disease, the highest titers were seen in the more advanced stages of liver damage. Thus, in addition to alcohol consumption, severity of liver disease may play a role in the appearance of circulating antibodies against acetaldehyde adducts.