Ribonucleic Acid Synthesis in Experimental Cardiac Hypertrophy in Rats

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Abstract
Cardiac hypertrophy was induced in rats by constriction of the aortic arch. Hearts from rats with aortic constriction increased in weight about 50% above those of control rats by 7 days after operation. RNA concentration increased between 24 and 48 hours after constriction and, thereafter, returned toward the control level. DNA concentration of hearts from rats with aortic constriction remained unchanged from that of sham-operated rats. Labeling of heart RNA with 32P was increased relative to that of sham-operated rats within the first 4 hours after aortic constriction. However, RNA labeling, relative to the labeling of AMP derived from ATP, increased above that of sham-operated rats only after 4 hours of aortic constriction and rose to maximum or near maximum values by 8 hours after operation. Various methods of extraction of RNA showed that the increase in labeling involved all the major species of RNA (28S, 18S, and 4S), and no evidence was found for the selective stimulation of a minority species. The nucleotide base composition of the various species of heart RNA of rats with aortic constriction was not significantly different from that of normal rats during the 4- to 8-hour period after operation. There was no terminal labeling of sRNA in hearts of either normal animals or those with aortic constriction.