Biochemical correlates of cardiac hypertrophy. II. Increased rate of RNA synthesis in experimental cardiac hypertrophy in the rat.

Cardiac hypertrophy was produced in rats by banding the ascending aorta. Increases in heart weight and RNA content occurred within 48 hours, indicating that hypertrophy develops rapidly. The total RNA content and the specific radioactivity of RNA labeled with H-uridine were determined. The rate of RNA synthesis was estimated from these data and from the specific radioactivity of the myocardial uridine nucleotide pool. The rate of RNA synthesis in hearts of banded animals averaged four times greater than controls on the second postoperative day and about two to three times greater on the fourth to fifth postoperative days. An expansion of the myocardial uridine nucleotide pool was observed in banded rats, but the size of the myocardial adenosine nucleotide pool was not changed. No changes in base composition of 28S, 18S, or 4S RNA were observed following cardiac hypertrophy. ADDITIONAL