DETECTION OF GLYCATED FETAL HUMAN LENS CRYSTALLINS BY CONCANAVALIN-A AND ALDEHYDE STAINING

The binding of the lectin Concanavalin-A (Con-A) to crystallins was in vestigated. For this purpose, human fetal and juvenile lens crystallin s were isofocused and specifically stained brown for glycoproteins by the lectin Con-A, and purple by the periodic acid Schiff's reagent (PA S). In reference experiments protein bands were stained with Coomassie Blue for proteins. Since Con-A is a protein with glucose-specific rec eptors, the following crystallins, glycated with this sugar, were visu alized after isoelectric focusing: HM-, beta(L),-, beta(S),- and gamma -crystallins, but not alpha(L),- and beta(H),-crystallins. Glycation i ncreased significantly with fetal age. The crystallins themselves coul d also function as sugar receptors, because it was shown that they pos sessed also receptors for glucose, like Con-A. This crystallin recepto r staining revealed beta(L),-, beta(S),-, gamma- but hardly HM-crystal lins. The PAS, Con-A and receptor stainings gave in principle identica l results. The glycoproteins Con-A, horseradish peroxidase and lentil lectins were used as positive controls. (C) 1997 Elsevier Science Irel and Ltd.