Heterogeneity in the compositon of human collagen

The imino acid composition of established collagens (liver, skin, tendon) and newly synthesized collagens (tumor in liver, cirrhotic liver, and dermal scar) in the same and different individuals has been studied. Whereas the hydroxyproline levels of tendon collagen and that of collagen derived from metastatic tumor nodules in liver of the same donor are similar, the proline levels were found to differ significantly. Thus isocollagens may exist in man. Hepatic metastasis collagen was identical to collagen derived from normal and cirrhotic liver. Furthermore, the levels of both imino acids of skin and scar collagen are similar and resemble those of tendon collagen from the same donor. From these studies, it appears that the imino acid components of collagen derived from a diseased organ resemble those of collagen from the same normal organ. Both imino acid levels appear to remain constant during aging of collagen and are independent of the donor's age at the time of new collagen synthesis.