Über die Beeinflussung der Wirkung von Coronardilatatoren durch die extracelluläre Calciumkonzentration (ein Beitrag zum Wirkungsmechanismus von Coronardilatatoren).

The effects of coronary dilatators were studied in isolated, isovolumetrically beating guinea pig hearts at different Ca-concentrations of the perfusion fluid. In all experiments hypoxic dilatation of the vessels was absent because the coronary venous partial pressure of oxygen was higher than 50 mm Hg. The coronary dilatation caused by six of the investigated substances-Nifedipine, Prenylamin, Verapamil, Lidoflazin, Dipyridamol and Hexobendin-could be suppressed by increasing of the Ca-concentration of the perfusion fluid. Therefore the mechanism of action on the smooth muscles of the coronary vessels has to be explained by a calcium antagonistic effect of these substances. The contractility of the myocardium is influenced in different ways. Nifedipine, Verapamil and Prenylamin show negative inotropic effects, which are also compensated by increasing the Ca-concentration. In contrast Hexobendin, Lidoflazin and Dipyridamol show no negative or even a small positive inotropic effect. The effects of nitroglycerine and carbochromen are not affected by changes of the extracellular Ca-concentration. [ABSTRACT FROM AUTHOR]