Skin collagen metabolism in the streptozotocin-induced diabetic rat: free hydroxyproline, the principal in vivo degradation product of newly synthesized collagen--probably procollagen.
We characterized the degradation products of recently synthesized collagen present in skins of control and diabetic rats. Specifically, the TCA-soluble fractions of homogenized skins from control and diabetic rats (killed 1 and 4 hours after [3H]-proline injection) were fractionated by molecular sieve chromatography, and eluted fractions were analyzed for hydroxyproline and [3H]-hydroxyproline. Free [3H]-hydroxyproline was the principal (greater than 95%), low molecular weight (greater than 2000 daltons), [3H]-hydroxyproline-containing material eluted from the molecular sieve column, this amount representing approximately 80% (controls) and approximately 87% (diabetics) of [3H]-hydroxyproline-containing material in TCA-soluble fractions of skin homogenates. These observations are similar to those from the intracellular degradation of cellular and secretory proteins in that the principal--almost exclusive--degradation product was the free amino acid. The free hydroxyproline had a greater specific radioactivity than that in any other [3H]-hydroxyproline-containing fraction (soluble and insoluble, see below); furthermore, the total radioactivity of free [3H]-hydroxyproline was greater at 1 hour than 3 hours later. These two properties (identity with free amino acid; time-dependent decrease in amounts) are consistent with [3H]-hydroxyproline arising from the intracellular degradation of procollagen. The [3H]-hydroxyproline-containing material eluting before free hydroxyproline (designated peptidyl [3H]-hydroxyproline) was similar to free [3H]-hydroxyproline in terms of specific radioactivity and the time-dependent decreases of specific and total radioactivities, these similarities indicating that the peptidyl [3H]-hydroxyproline are intermediates in the degradative pathway of procollagen to free amino acids. Results for control and diabetic rats were qualitatively similar, with regard to the inter-fraction ratios of specific radioactivities and their time-dependent changes. However, the degradative process, as assessed by the release of free and peptidyl [3H]-hydroxyproline, was dramatically enhanced by the diabetic state, extending our previous results based on analyses of uncharacterized degradation products.
D000818:Animals; D001345:Autoradiography; D002850:Chromatography, Gel; D003094:Collagen / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D006909:Hydroxyproline / Q000378:metabolism*; D008297:Male; D011347:Procollagen / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000378:metabolism*; D014316:Tritium
D011347:Procollagen; D014316:Tritium; D003094:Collagen; D006909:Hydroxyproline