THE RELATION OF ENDOGENOUS CATECHOLAMINE TO THE ACTION OF STROPHANTHIN-G ON ATRIAL CONTRACTIONS OF RABBITS AND GUINEA-PIGS

Abstract

It is generally accepted that the remarkable effect of digitalis on heart falure is caused by its specific action on the contractile mechanism of the heart muscle. The mode of pharmacological action of digitalis glycosides have been studied by many investigators, and it has been claimed that digitalis might have some influence on the energy production mechanism of the heart. The metabolic pathway of heart muscle contraction is not positively influenced by digitalis glycosides, though they do bring about an increase in contractile force [Wollenberger (1), Bing et al. (2, 3)]. Szent-Gyorgyi (4) reported that actomyosin is influenced by ATP and inorganic ions but not by digitalis. However, it has been reported that ATP-ase activity in the muscle cell membrane of rat hearts is promoted by digitalis in therapeutic dosage [Repke (5)]. On the other hand, Hadju and Szent-Gyorgyi (6) reported that the decrease in K-ion concentrations in the heart muscle induces an increase in contraction, and digitalis augments an efflux of the K-ions in the heart muscle. On contrary, Klaus et al. (7) reported that the influx of 42K-ions into the heart muscle cells was increased by digitalis in therapeutic doses. The cardiac action of digitalis has been explained by some investigators as that of an autonomic drug due to the result that digitalis increases adrenaline action [Donielpolu (8), Fujita (9)]. Our experiment were carried out to discover the relation of digitalis action to endogenous catecholamine mobilization in the atria from the standpoint that the catecholamines in heart muscle are mostly in a bound form and the contractile function of heart is controlled by the released catecholamine available.