A comparison of the rates of synthesis and turnover of collagen and non-collagen proteins in adult rat periodontal tissues and skin using a microassay

Abstract

The metabolic activity of collagen in rat molar periodontal tissues was measured by following the incorporation of [ 3H]-proline into hydroxyproline. The sensitivity of the assay method allowed the rates of collagen to be determined in tissue samples taken from individual animals. The rate of synthesis of collagen in periodontal ligament was twice as fast as attached gingiva, four times as fast as skin corium, used as a reference tissue, and six times as fast as alveolar bone. Incorporation of proline label into mature collagen was highest in periodontal ligament, which had a rate five times faster than attached gingiva, six times faster than the bone and 15 times faster than skin. A comparison between the rates of incorporation of label into newly synthesized collagen and into mature collagen in each tissue indicated that newly synthesized collagen in periodontal ligament and bone was quantitatively converted into insoluble collagen, but in attached gingiva and in skin a conversion efficiency of 50 and 33 per cent respectively was found. The half-lives of newly synthesized collagen were calculated as 24 min for alveolar bone, 40 min for periodontal ligament, 80 min for gingiva and 360 min for skin. The half-lives of the turnover of the mature collagen were 1 day in periodontal ligament, 5 days in gingiva, 6 days in alveolar bone and 15 days in skin corium. The mature collagen half-lives were generally shorter than published values and suggest that recycling of labelled amino acids may affect results using conventional methods. The incorporation of [ 3H]-proline into non-collagenous proteins soluble in 0.45 M sodium chloride showed an overall low metabolic activity for these proteins compared to collagen. However, there is some evidence of highly active non-collagenous proline-containing components insoluble in 0.45 M sodium chloride salt and 0.5 M acetic acid.