Collagen metabolism during right ventricular hypertrophy following induced lung injury

Collagen synthesis and degradation rates were estimated in ventricles of normal rabbits and in those with right ventricular hypertrophy resulting from bleomycin-induced lung injury. Synthesis rates were estimated from the radioactivity in tissue [14C]hydroxyproline following a single intravenous injection of [14C]proline with a "flooding" dose of unlabeled proline (Biochem. J. 206: 535-544, 1982). The rate in the left ventricle was 5.8 +/- 1.0 compared with 2.9 +/- 0.4%/day in the right (P less than 0.02). Degradation rates, based on [14C]hydroxyproline levels in the tissue-free pool, indicated that in both normal ventricles about one-third of newly produced collagen was degraded rapidly following its synthesis. Six days after bleomycin, right ventricular collagen content fell by 35%, associated with a marked increase in tissue-free hydroxyproline levels. After 14 days the right ventricular weight and collagen content had increased by 49.4 +/- 3.7% (P less than 0.001) and 31.7 +/- 4.4% (P less than 0.05), respectively, and collagen synthesis rates increased to 9.7 +/- 1.8%/day (P less than 0.001). It is concluded that collagen is synthesized and degraded quite rapidly in normal heart tissue but that fractional rates differ between ventricles. The evidence also suggests that increased collagen synthesis and breakdown of mature collagen occurs as the connective tissue matrix is remodeled during adaptive cardiac growth.