Experimental Hypertrophy Without and With Digitalization on Creatine Content of Rabbit Hearts. ∗

In the type of cardiac hypertrophy resulting from nutritional anemia, 1 or following thyroid administration, 2 produced in rats, the percentage of creatine in the heart muscle has been found to drop; the total amount of creatine in the whole heart seemed to remain the same, the percentage decreasing as the heart muscle increased in weight. In a preliminary note, 3 we have recorded the creatine values in hearts in which hypertrophy has been produced by a different method. Using rabbits, the aortic leaflets were torn or punctured, thus producing experimental aortic regurgitation. The degree of hypertrophy has been determined by comparing the Heart-weight/Body-weight ratio with our previously established normal value. 4 The animals were of nearly the same age, and weighed around 3,000 gm. at the completion of the experiment. Creatine determinations were made following the technique of Seecof, Linegar and Myers. 5 In Table I summarized are the creatine values for the completed series of these animals. Some of them have been digitalized, in order to note the effect of this drug on hypertrophy; the remainder have had no digitalis. A control group was injected with digitalis, without having been operated upon.

In animals weighing from 2,500 to 3,500 gm., the normal hearts contain 176 mg.% creatine, with a standard deviation of 15.8 mg.%. Solids average 22.1%, S. D. 1.4%. The creatine calculated on the basis of dried weight averaged 825 mg.%±80 mg.%. In the hypertrophied hearts, the average value is slightly higher, with a tendency for the higher values to be found in hearts with moderate hypertrophy, dropping to normal or slightly below as the grade of hyper trophy increased. This means that the absolute amount of creatine in such hypertrophied hearts is definitely increased.

In those digitalis control animals who received 0.1 cat unit twice weekly, injected as Digalen or Digifoline, there was a distinct increase in the cardiac creatine content. Those that received larger doses, namely 0.3 or 0.5 cat unit, showed no relative elevation.