METABOLIC ACTION OF THE CARDIAC GLYCOSIDES I.

The search for an explanation of the mode of action of the cardiac glycosides has led a number of authors to examine the influence of this important group of cardiac drugs on the energy-yielding processes in the heart. The great majority of these investigations has dealt with effects on the energy metabolism, particu larly the respiration, of the heart in vivo. Only few attempts have been made to relate the cardiotonic and cardiotoxic properties of the cardiac glycosides to an ability of producing changes in the respiratory activity of heart muscle in vitro, i.e. changes independent of those in mechanical activity. FrÃhauf(l) reported that the cardiac glycoside strophanthin inhibited the oxygen uptake of minced mammalian heart muscle. Salomon and Riesser (2), who repeated some of FrÃhauf'sexperiments, failed to observe any effect of low or high concentrations of strophanthin and digitoxin. Similar experiments of Genuit and Haarmann (3) likewise yielded negative results. All these studies are open to criticism, because without exception the rates of oxygen consumption were abnormally low