CHANGES IN THE GLYCOFORMS OF RAT ALPHA-1-ACID GLYCOPROTEIN DURING EXPERIMENTAL POLYARTHRITIS

We analyzed the carbohydrate moiety of purified alpha-1-acid glycoprot ein (AGP) from Lewis adult male rats that were healthy (AGPh) or had e xperimental polyarthritis (AGPi). Sodium dodecyl sulfate polyacrylamid e gel electrophoresis before and after N-glycanase treatment showed th at AGPi had a slightly lower molecular mass (43 kDa vs. 45 kDa for AGP h) due to a lesser carbohydrate content. Carbohydrate analysis of puri fied AGP showed a slight decrease in the sialyl and galactosyl molar r atio in polyarthritis. However, the same difference in AGPh and AGPi ( i.e. 0.6 residue) between the sialyl and galactosyl molar ratio indica ted more than one sialyl residue per complex-type branch. Affinity for concanavalin A (ConA) of the whole glycoprotein and released oligosac charides showed a progression during polyarthritis towards more reacti ve glycoforms or more ConA-bound oligosaccharides. Anion-exchange HPLC of the ConA-fractionated oligosaccharides corroborated the decreased sialylation in polyarthritis. Taken together, these results suggest a fall in branched and sialylated oligosaccharides during experimental p olyarthritis. These structural changes might be related to an increase in Gal beta 1-4GlcNAc alpha 2-6 sialyltransferase activity described elsewhere in inflammatory states.