Abstract
Effects of aminophylline, proxyphylline and a proxyphylline-Melilotus extract-rutin-mixture (theoesberiven) on the heart and coronary circulation were studied in the canine heart-lung preparation supported by a donor in comparison with those of isoproterenol (Isp). All the three methylxanthines produced an increase in the coronary flow associated with a definite positive inotropic effect. In contrast to the effects of Isp, increase in the heart rate was minimal with these compounds. Myocardial redox potential (ΔEh) changed to more negative values, although the changes were smaller than that produced by Isp. Since it was found that these substances produced a disproportionately greater increase in the coronary flow as compared with an increase in the myocardial oxygen consumption, the effects of these substances on the myocardial high-energy phosphate compounds were also studied in the isolated perfused heart preparation of the guinea pig. All the three compounds produced a reduction of the creatine phosphate (Cr-P)/(Cr-P+Inorganic phosphate) ratio and the energy charge of the adenylate system, in the following order, aminophylline>proxyphylline=theoesberiven. Antagonism towards adenosine was found with the three methylxanthines used. In the isolated left atrial preparation of the guinea-pig, aminophylline induced a definite potentiation of the positive inotropic effect of isoproterenol, while the potentiation produced by proxyphylline and theoesberiven was minimal.
