Similarity of the carbohydrate moieties of fibronectins derived from blood plasma and synthesised by cultured endothelial cells

Plasma and cellular fibronectins are reported to be very similar but not identical in chemical structure. We have compared bovine plasma fibronectin with fibronectin secreted by bovine aortal endothelial cells in culture. Techniques were chosen to highlight likely structural differences, particularly in the carbohydrate moieties. Both fibronectins were wholly reactive to monospecific antiserum and behaved identically in two-dimensional gel electrophoresis. The oligosaccharide chains were identical in proportion and degree of sialylation by anion-exchange HPLC. Fractionation of the glycopeptides on immobilised lectins and serotonin showed that both fibronectins contained (i)_predominantly biantennary oligosaccharides, (ii) exclusively N-acetylneuraminic acid residues in a non-clustered array and (iii) no L-fucose residues. The overriding structural similarities support the proposal that the endothelium is a site of synthesis of plasma fibronectin in vivo.