The identification of two types of collagen in the articular cartilage of postnatal chickens

Abstract

Amino acid analyses of carefully dissected samples of the articular cartilage of postnatal chickens indicates the presence of significant amounts of a collagen with a low hydroxylysine content. It was found that 9 M LiCl solutions preferentially extract the components of a collagen whose components when identified by ion exchange chromatography and amino-acid analyses, established that they were derived from Type I collagen. Type II collagen was essentially insoluble in solutions of 9 M LiCl, but could be solubilized in 4 M CaCl2 after prior treatment of the cartilage with pepsin. The αl (II) components were then isolated and characterized by their behavior during ion exchange chromatography and by their amino acid composition. The findings establish that the articular cartilage of postnatal chickens contains substantial amounts of Type I collagen and suggest that the nature and stability of the crosslinkages in Type I collagen of cartilage differs significantly from those of Type II collagen of cartilage. Moreover, it is also postulated that the nature of the major intermolecular cross-linkages in the Type I collagen of cartilage are similar to those present in Type I collagen of bone rather than those present in the Type I collabens of skin and other connective tissues.