Reactivity of IGF binding protein-3 isoforms towards concanavalin A in healthy adults and subjects with cirrhosis.

The capacity of the liver to synthesize insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) may be compromised by alcohol. The characteristics of IGFBP-3 variants obtained from healthy individuals and patients with alcoholic cirrhosis (ALC) were compared. Concanavalin A (Con A) affinity electrophoresis and ligand blotting demonstrated that there was a gradual change in carbohydrate properties of putative IGFBP-3 with progression of ALC from stages A to C. As many as 12 ionic species of IGFBP-3 could be distinguished, corresponding probably to variously glycosylated and/or phosphorylated isoforms of the core protein. Three of them reacted significantly with the immobilized Con A, the pattern being altered in patients with ALC. Patients with ALC in stage B exhibited the presence of clearly differentiated IGFBP-3 variants less and more Con A reactive, suggesting this stage to be a turning point with the most intensive changes in the IGF - IGFBP system. Because the glycosylation pattern is tissue specific, pathological post-translational modifications found for one glycoprotein (IGFBP-3) are probably shared by others of the same tissue origin. This may affect their susceptibility to proteolysis and subsequently their function.