Abstract
Summary
Experiments designed to investigate the action of nicotinic acid on the isolated rabbit's heart are reported. Dilutions of from 1:100,000 to 1:2,000,000 were employed, and careful attention was paid to constancy of temperature and hydrogen-ion concentration.
It was found that the effect of nicotinic acid on well functioning hearts is insignificant. In the case of failure of the myocardium, however, this pyridine derivative causes a marked increase in amplitude of the cardiac excursion, reversal of abnormal rhythms (including partial heart block, ventricular ibrillation, and ventricular stand-still), and at times a considerable augmentation of coronary flow. In no case does it appear to have an unfavorable influence.
The explanation of these effects may lie in the role played by nicotinic acid in carbohydrate metabolism. The idea is advanced that the observed disturbances of myocardial action are due to inactivation or depletion of the pyridine nucleotides by the anoxia incident to experimental technic; and that restoration of normal function probably depends on correction of this temporary and reversible deficiency by the addition of nicotinic acid to the perfusion fluid.
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