Modifications of concanavalin A patterns of alpha 1-acid glycoprotein and alpha 2-HS glycoprotein in alcoholic liver disease.

In order to test whether abnormalities in hepatocytes affect the glycoprotein carbohydrate moiety, crossed immunoaffinoelectrophoresis (CIAE) with Concanavalin A (Con A) was used to study serum alpha 1-acid glycoprotein (alpha 1-AGP) and alpha 2-HS glycoprotein (alpha 2-HS) obtained from alcoholic patients with biopsy-proven liver disease. Cirrhotic patients, placed in groups C1, C2 or C3, according to Pugh's classification, were compared to healthy donors (N) and to steatosic non-cirrhotic patients (S). Con A CIAE patterns revealed in group N three subpopulations for alpha 2-HS and four for alpha 1-AGP. Two main results emerged from this study: (1) in the alcoholic groups, the proportions of Con A-unreactive subpopulations of both glycoproteins increased. Moreover, group N could be separated from group S and group S from all the cirrhotic groups. (2) There was a good correlation between the relative amounts in Con A-unreactive subpopulations of alpha 1-AGP and alpha 2-HS. The increases observed in Con A-unreactive subpopulations are probably a general phenomenon related to alterations in glycosylation processing during liver cell damage.

Evaluation of the degree of desialylation of serum C1-inactivator and haemopexin.

The calibration curves for evaluating the degree of desialylation of C1-inactivator (sialic acid content 12.5%) and haemopexin (sialic acid content 4%) have been plotted. No desialylation of either glycoprotein occurs in normal subjects. In the patients (liver damage) studied, C1-inactivator is often desialylated, whereas haemopexin is not. In a previous report, we had shown that alpha1-acid glycoprotein is more often desialylated than alpha1-antitrypsin. Thus, it appears that the degree of desialylation of the sialic acid-rich glycoproteins is a more sensitive index of the severity of hepatic injury than that of the sialic acid-poor glycoproteins. This could be due to a defect in the sialylation process during synthesis.

Evaluation of the degree of desialylation of serum alpha 1-acid glycoprotein and alpha 1-antitrypsin.

A method for evaluating the degree of desialylation of alpha 1-AGP and alpha 1-AT has been developed. It consists in their simultaneous determination by radial immunodiffusion (RID) and electroimmunodiffusion (EID). When a desialylation exists, an underestimation by EID relative to RID is found. (1) No significant desialylation of alpha 1-AGP and alpha 1-AT occurred in normal subjects. (2) No correlation between desialylation of alpha 1-AGP and alpha 1-AT and their amounts existed. (3) Desialylation was preferentially observed in patients with severe hepatic damage but also with inflammatory disorders.

Involvement of sialic acid residues in electroimmunodiffusion of alpha 1-acid glycoprotein. A method for determining the degree of sialylation of serum glycoproteins.

When the two immunological methods, radial immunodiffusion (RID) and electroimmunodiffusion (EID), were used for the determination of alpha 1-acid glycoprotein, a significant discrepancy in the results was encountered depending on the degree of sialylation. It appeared that with desialylated alpha 1-acid glycoprotein, amounts estimated by EID were much lower than those actually present as assayed by the RID method. Determination of glycoprotein samples treated with neuraminidase for varying periods of time revealed an increasing underestimation by the EID method with decreasing sialic acid content. Partial resialylation of asialo-alpha 1-acid glycoprotein by bovine colostrum beta-galactoside alpha (2 leads to 6) sialyltransferase on the other hand resulted in less underestimation. Differential determination of alpha 1-acid glycoprotein by the two immunological methods thus offers a method for the estimation of the degree of sialylation of alpha 1-acid glycoprotein and other sialoglycoproteins in serum and body fluids.