Collagen metabolism in the myocardium of normal and diabetic rats.

Myocardial collagen and total protein synthesis were studied in normal, diabetic, and insulin-treated diabetic rats after a single intraperitoneal injection of L-[2,3-3H]proline as a radioisotopic precursor. The incorporation of tritiated proline into myocardial protein was regarded as a measure of total protein synthesis and the incorporation into hydroxyproline as indicative of myocardial collagen synthesis. Both total protein and collagen synthesis were found to be significantly lower in diabetic rats. This was associated with decreased degradation of both total protein and collagen in diabetic rats, as suggested by prolonged turnover times. Collagen content was also found to be increased in diabetic myocardium. Early insulin therapy with normalization of blood sugars in diabetic rats returned myocardial collagen metabolism to normal. This suggests that maintenance of euglycemia in diabetic rats is necessary to prevent abnormal myocardial collagen metabolism.