Collagen accumulation in the neonatal rat skin: absence of fibrillar collagen degradation during normal growth.
Collagen-bound collagenase activity was assayed in the entire skins of growing neonatal rats. The levels of fibrillar collagen degradation were found to be extremely low throughout the first six days of life. Less than one percent of the collagen accumulated during one day's growth could be degraded by the collagenase bound to the extracellular fibrils of the skin. Control experiments, which included the addition of purified rat uterine collagenase to the skins both before and after homogenization, showed that collagenase activity is easily detectable in the tissue when it is present. It therefore appears that the vast majority of skin collagen, once deposited as fibrils in the skin, fails to turn over during growth. Support for this concept was provided by experiments in which neonatal animals were injected with the potent synthetic glucocorticoid, triamcinolone. Very low levels of collagen-bound collagenase, comparable to those observed in control animals, were found in the steroid-treated animals. Furthermore, the inhibition of collagen synthesis in these animals resulted in a constant chemical content of collagen as well as a constant amount of proteinaceous [14C]-hydroxyproline after injection of [14C]-proline over a 72-hour period. Our results strongly suggest that the bulk of fibrillar collagen does not participate in a dynamic equilibrium between synthesis and degradation during normal neonatal growth. In addition, the results in steroid-treated animals suggest that the rate of collagen accumulation during this period appears to be essentially a function only of collagen synthesis.
Jeffrey
J J
JJ
Di Petrillo
T
T
Counts
D F
DF
Cutroneo
K R
KR
D000818:Animals; D000831:Animals, Newborn; D003094:Collagen / Q000378:metabolism*; D006909:Hydroxyproline / Q000032:analysis; D003012:Microbial Collagenase / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D014221:Triamcinolone / Q000494:pharmacology
D014221:Triamcinolone; D003094:Collagen; D003012:Microbial Collagenase; D006909:Hydroxyproline