Cold-Insoluble Globulin (Fibronectin), IV Affinity to Soluble Collagen of Various Types

Abstract

The binding of native and denatured soluble collagen, Type I, II and III, by fibronectin was measured in various systems using 125I-labeled collagen preparations. Soluble Type I and II collagens had been extracted from fetal calf skin. Soluble Type II collagen was prepared from joint cartilage of fetal calves. Fibronectin (cold-insoluble globulin) was prepared from human plasma. Among the samples investigated, denatured Type III collagen showed the strongest affinity to fibronectin. It was followed by the denatured Types I and II, which were nearly equally effective. The affinity of fibronectin to native soluble collagen was demonstrated by the adsorption assay and the radioactive binding assay only for the Type III preparation. It was considerably lower than those of the denatured samples. The affinity of native Type I and Type III collagen was only detectable by the inhibition assay, using very high concentrations. Native Type II collagen gave nuclear results in this assay. The meoderate affinity of native Type III collagen and fibronectin might be of importance for processes taking place in atherosclerosis. Type III collagen is found in blood vessels immediately beneath the epithelium layer.