Studies about the effects of positive inotropic and vasoactive substances.

The present study describes an in vitro method to characterize inotropic and vascular effects of compounds on isolated human cardiovascular tissues. In vitro, the positive inotropic effect in electrically driven left ventricular papillary muscle strips of nonfailing and failing human myocardium was studied and compared to experiments performed in muscle preparations of guinea pigs. In radioligand binding experiments the receptor subclasses mediating the inotropic effects were characterized. In isolated coronary or pulmonary artery rings from man the effect on vascular tone could be investigated. These data show that inotropic responses for dopamine and isoprenaline in guinea pig differ from those in the failing human myocardium. Therefore, new cardiovascular effective agents should be screened in human myocardial tissue, as experimental results from other sources may be irrelevant in this respect.