Digitalization of the myocardium in the intact animal by direct coronary arterial drug administration: II. Relation of the rate of administration to myocardial concentration and toxicity☆

Abstract Experiments were designed to study the relation of the concentration of 3 H digoxin perfusing the coronary vessels to the myocardial concentration of the drug. 3 H digoxin, in concentrations ranging from 1.27 to 20 μg/ ml, was perfused into the left anterior coronary artery of 25 anesthetized dogs at a constant infusion rate of 0.51 ml/min. At various times the dogs were sacrificed and the myocardium analyzed for radioactivity. The major determinant of the mean rate of myocardial uptake of tritiated digoxin appeared to be the concentration of the infused glycoside. The total uptake of 3 H digoxin was dependent upon concentration of coronary 3 H digoxin and the duration of infusion. These data elucidate some of the factors that determine the myocardial concentration of digoxin.