Collagen turnover in isoproterenol-induced DNA synthesis and its modification by x-ray irradiation

Collagen metabolism in mouse salivary glands during the prereplicative phase of DNA synthesis induced by a single injection of isoproterenol was compared to that in liver and kidney where the cells do not respond to isoproterenol with increased DNA synthesis. Collagen prelabeled with [3H]proline degraded rapidly in submandibular gland following isoproterenol injection. This was consistent whether the decrease in specific activity of prelabeled collagen or in collagen content per mg DNA was measured. Collagen synthesis following degradation increased prior to onset of DNA synthesis in both parotid and submandibular glands, and later resulted in an increase in net collagen content per gland. The increase in collagen synthesis was abolished in both glands when mice had been irradiated with X-ray or injected with cycloheximide to inhibit the onset of the DNA synthesis. These changes were not detected in either liver or kidney. Thus both degradation and synthesis of collagen seemed to be correlated to the events leading to isoproterenol-stimulated DNA synthesis of epithelial cells in vivo.