An immunochemical procedure to evaluate the degree of desialylation of alpha 1-acid glycoprotein in rat serum.

When radial immunodiffusion (RID) and electroimmunodiffusion (EID) were used for the determination of rat alpha 1-acid glycoprotein (alpha 1-AGP) a significant discrepancy in the results was encountered depending on the degree of sialylation. When alpha 1-AGP was desialylated, the amounts estimated by EID were much lower than those actually present as assayed by the RID method. The relationship between the percentage of desialylation of alpha 1-AGP and the percentage of its underestimation by EID relative to RID was determined and a calibration curve was plotted to evaluate the degree of desialylation of rat alpha 1-AGP. When compared to other procedures (rat membrane inhibition assay and isoelectrofocusing), the proposed method was easier to perform and allowed the specific evaluation of the degree of undersialylation of the glycoprotein.