Regulation by heparin and hyaluronic acid of the fibronectin-dependent association of collagen, Type III, with macrophages.

Trypsinized peritoneal macrophages of guinea pigs moderately bound soluble native 125I-collagen, type III. The association was slightly improved by plasma fibronectin. An additional considerable enhancement was achieved by heparin or heparan sulfate in presence of fibronectin. The enhancing effect of the two N-sulfated glycosaminoglycans was observed over a broad concentration range and, in case of heparin, exhibited a maximum near 1 mg/ml. Further rise of concentration resulted in a decline of binding. The related heparan sulfate potentiated binding less effectively than heparin. Optimal efficiency was recorded with lower concentrations. Hyaluronic acid, in higher concentrations, suppressed the enhancing effect of heparin or heparan sulfate on collagen binding. The improved attachment of native collagen, type III, to cells in presence of fibronectin and N-sulfated glycosaminoglycans was explained by a heparin/heparan sulfate induced conversion of soluble fibronectin to fibrils which showed an increased affinity to rod-like collagen molecules as well as to cell-surface structures. Hyaluronic acid, probably, inhibited the interaction of fibronectin fibrils with these substrates. Heparin and heparan sulfate, also in the absence of fibronectin, improved within a limited concentration range the binding of native 125I-collagen, type III, to the cells. The amount attached was, however, considerably less than in presence of fibronectin.