Myocardial nucleic acid synthesis following constriction of the aorta in rats.

Abstract

The time course of changes in content and labelling of nucleic acids in the ventricles was examined during the development of cardiac hypertrophy. Analyses were made 4 hours to 4 weeks after the constriction of the abdominal aorta in rats. Between 2 and 7 postoperative days, there were significant increases in RNA concentrations per g of tissue as well as in the total RNA and DNA contents in both ventricles. Incorporation of [8-14C]adenine into ventricular RNA expressed as the specific activity (dpm/mg RNA) increased steeply following constriction, reaching its peak in 1 to 2 days. The activity declined equally rapidly thereafter. The specific activity of ventricular DNA (dpm/mg DNA) reached an extremely high peak on the second day, then decreased slowly over a period of 2 weeks towards the preconstriction level. The pattern of changes in labelling of ventricular nucleic acids was similar in both ventricles during the experimental period. The incorporation of lecine into ventricular proteins was increased also. It is concluded that the rate of synthesis of RNA increases abruptly following constriction of the abdominal aorta in rats, followed by an increase in DNA, suggesting the existence of two types of the adaptation process; the initial response by cardiac muscle and interstitial cell components, and the prolonged mesenchymal cell proliferation.