Rat fibrosarcoma as a source of stable co-polymer of type I and type III collagens.

During conventional procedures for the extraction of collagen from rat fibrosarcoma it was observed that a significant fraction of the acid-soluble collagen remained insoluble when subsequently fractionated at neutral pH. Analysis of this collagenous component, using amino acid analysis, cyanogen bromide peptide mapping, proteinase susceptibility and the action of denaturing and reducing agents, revealed different properties when compared to other collagen species. The results indicate that the tumour collagen fraction is probably a stable complex of type I and III collagens. This native collagen heteropolymer represented approximately 18% of the total collagen from rat fibrosarcoma and as such provides a unique natural source of this collagen complex for further analytical studies.