Collagen and muscle protein synthesis during cardiac hypertrophy in the dog.

The fractional synthesis rates of collagen and noncollagen protein in the right ventricle of the dog have been measured during hypertrophy after pulmonary artery stenosis. The synthesis rates of noncollagen protein were the same using a continuous infusion of either [14C]tyrosine or [14C]proline, and increased from 7.6% per day in the normal ventricle to 13.6% per day after 1 day of stenosis. This level was maintained at 5 days, but by 12 days stenosis had declined to near normal values. The increase in synthesis rate could almost entirely account for the increase in mass of the right ventricle (83%) that occurred after 24 days of hypertrophy. The synthesis rate of collagen in the normal myocardium was very slow, 0.64% per day, but after 5 days of hypertrophy increased sixfold to 4.0% per day, and was still elevated after 12 days of hypertrophy.