Type IV collagen antigens in serum of rats with experimental fibrosis of the liver.

Specific and sensitive radioimmunoassays for the N-terminal (7S-collagen) and C-terminal (NC 1) crosslinking domains of type IV collagen were used to study the effects of prolonged treatment of rats with CCl4 on the concentrations of these antigens in serum. After four to six weeks of CCl4 treatment a highly significant increase of type IV collagen antigen levels in serum was to be seen. These elevated levels exhibited a significant correlation to the increased amounts of hydroxyproline in liver samples, when the samples were taken during CCl4 treatment. Analysis of the molecular weight distribution of serum antigens by gelfiltration revealed for 7S-collagen a bimodal distribution, whereas NC 1 eluted mainly as one peak. This peak coeluted with the high molecular weight peak of 7S-collagen, suggesting that this peak might represent intact type IV collagen. The lower molecular weight peak of 7S-collagen antigen eluted at a position which was comparable to standard 7S-collagen. Determination of type IV collagen antigens in serum might be of diagnostic usefulness for the follow up and treatment control of hepatic fibrosis.