Metabolism of rat skin collagen: the effect of arrested development and subsequent catch-up growth on the stability of the connective tissue fibers.
The growth of 33 day-old rats was temporarily arrested by feeding a low-protein diet for 6 weeks. The skin collagen hydroxyproline was labelled previously at 31 days by giving a single intraperitoneally injection of L-[5-3H] proline. This label was rapidly incorporated during the subsequent 2 days of normal growth and then remained at a steady level in the skin collagen when growth was halted. Control animals continued to incorporate label for 2 weeks and then the level of [3H] hydroxyproline declined as this label was subsequently lost from the skin collagen. During arrested development, the skin collagen became increasingly insoluble and the analysis of reducible crosslinks revealed a pattern similar to the collagen of an older animal. In addition the isometric tension developed per unit mass of collagen during thermal denaturation was three-fold greater than that from the age-matched control animals. Refeeding the normal diet gave an immediate burst of rapid growth. The pre-labelled collagen did not turnover during this period since there was no significant change in the level of labelled hydroxyproline in the skin. The newly synthesized collagen, which diluted out these older fibers, appeared to be immature, since it was initially rich in type III, it was very poorly crosslinked, and it caused a fall in the isometric tension value. It was concluded that there need not be limited degradation of the older collagen fibers in skin as an a priori requirement for growth.
D000375:Aging; D000818:Animals; D003094:Collagen / Q000378:metabolism*; D003238:Connective Tissue / Q000378:metabolism / Q000502:physiology*; D006130:Growth Disorders / Q000209:etiology / Q000378:metabolism*; D008297:Male; D011392:Proline / Q000378:metabolism; D011488:Protein Deficiency / Q000150:complications / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000378:metabolism*
D003094:Collagen; D011392:Proline