Chemical changes associated with aging of collagen in vivo and in vitro

Abstract

Collagen extracted from rat skin by neutral-salt solutions contains less aldehydes than the more insoluble collagen fractions. The concentration of aldehydes in collagen is directly related to its capacity to form stable cross-linked gels, which do not redissolve on cooling and become more insoluble in a variety of reagents. Whereas the absorption spectrum of neutral-salt-soluble collagen treated with N-methylbenzothiazolone hydrazone resembles that of acetaldehyde, the more insoluble collagen fractions show increasing amounts of a component that behaves like an αβ-unsaturated aldehyde. The ratio between α- and β-sub-units present in a particular fraction of soluble collagen seems to be constant and independent of the age of the animal. Neutral-salt-soluble collagen, which has a low concentration of β-components, will generate intramolecular bonds if gelled at 37°. These intramolecular bonds seem to precede the formation of stable intermolecular cross-links, since these gels can redissolve when cooled to yield a soluble collagen with a higher content of β-components of intramolecular origin.