Soluble and insoluble collagen and elastin in the rat hair cycle.

Soluble and insoluble collagen and elastin were chemically evaluated in the dorsal skin of rats during the third hair cycle. Both fractions of collagen remain unchanged during anagen, while they increase considerably in the first days of telogen to drop afterwards. Elastin content gradually increases throughout anagen and falls in telogen. The authors suggest that the increasing amounts of collagen in the first part of telogen may be responsbile for the progressive block in the downwards movements of previously growing follicles into the dermis. Elastin data could be the result of a mechanical readjustment of skin to the expansion provoked by growing follicles.