Age-related changes in the content of the collagen crosslink, pyridinoline.

Pyridinoline is a crosslinking amino acid of collagen fibers. The age-related changes in the content of pyridinoline were followed for collagens from human and rat costal cartilage and Achilles tendon. The pyridinoline content of the collagens in fetal or newborn animals was very low and increased markedly with growth of the animals. In rat tissues, the pyridinoline content continued to increase after the animal had reached maturity. On the other hand, in human tissues, it began to decrease after about 30 years of age. Pyridinoline may serve as an interesting index for the aging of connective tissues.