| Popis: |
In the classic studies of Straub (1910), as well as Clark (1937), one finds the first attempts to show a relationship between the localization of cardiac glycosides by cardiac cells and their effect on the heart. Thus, Straub’s early experiments showed that excised frog heart contained certain receptive sites which bound a fatal concentration of digitalis from the perfusate. Furthermore, it was observed that the receptive capacity of heart muscle became saturated after one passage of digitalis through it, provided the perfusate concentration of this drug was sufficiently high. On the other hand, by meticulous calculations, Clark showed that since it took 2 μg of ouabain to arrest a frog ventricle weighing 1 g and containing 3 × 108 cells, the lethal effect was due to the fixation of 107 ouabain molecules per cardiac cell. He also pointed out that the fixed ouabain molecules could not cover more than 3% of the surface of the cardiac cell. |
