Collagen synthesis in explants from rat intestine.

Collagen is the major structural component of the intestinal wall and its metabolism is of special interest for intestinal strength. We describe collagen synthesis in short-term (3 h) incubations of rat intestinal tissue, as measured in terms of incorporation of [3H]proline in collagenase-digestible protein and percentage relative collagen synthesis. In this time span, incorporation of [3H]proline in collagen increases linearly with time and tissue weight. Addition of unlabeled proline during incubation, in excess of the 0.1 microM [3H]proline always present, strongly increases both total protein and collagen synthesis, suggesting that proline transport is rate limiting. Further experiments have been performed in the presence of labeled proline alone and with the addition of 0.35 mM unlabeled proline. Collagen synthesis is significantly higher in colon than in ileum, comprising 0.37 and 0.21%, respectively, of total protein synthesis. Also, collagen synthesis decreases considerably with age, both in ileum and colon. The results presented here demonstrate that rat intestinal explants synthesize measurable amounts of collagen in vitro and that the system used is able to detect changes in in vivo synthetic capability such as those induced by ageing.