[Properties and conditions of formation of the fibronectin-collagen complex in a culture of human embryo fibroblasts].

In our previous study the macromolecular complexes mostly consisting of fibronectin and procollagen were isolated from human fibroblast culture media using immobilized antibodies against fibronectin. At present an attempt was made to elucidate at what stage the formation of the fibronectin-collagen complex occurs--either in the course of incubation of the immobilized antibodies with labelled proteins secreted by fibroblasts, or in the extracellular space while labelling fibroblasts, or intracellularly. The results obtained show that the fibronectin-collagen complex: 1) pre-exists even before incubation with the immobilized antibodies and 2) it is of intracellular origin. Thus, the considerable amount of the fibroblast-secreted fibronectin (no less than 20%) is released from the cell not in the free form but in the complex with procollagen. It was suggested that the fibronectin-collagen complex presents a stage in the formation of the insoluble extracellular matrix.