Abstract
The effects of calcium (-)-N-[(S)-3(N-cyclohexylcarbonyl-D-alanyl)-thio]-2-methylpropion]-L-prolinate (MC-838, altiopril calcium), an in-hibitor of angiotensin converting enzyme, were investigated in 9 isolated atrial preparations and 7 intact anesthetized donor dogs. In 7 intact dogs, 1-10mg/Kg of MC-838 caused a decrease in systemic blood pres-sure, but no significant influence on heart rate was observed. At the same time, in isolated atria perfused with donor's blood, significant in-creases in developed tension and slight increases in sinus rate were observed with 3 and 10mg/Kg of MC-838. Intraarterial MC-838 at 10-300μg did not induce significant cardiac effects and MC-838 at 1-3mg caused an increase in developed tension and a slight increase in sinus rate. The positive inotropic and chronotropic effects were not blocked by adequate doses of propranolol, which significantly blocked norepinephrine-induced positive chronotropic and inotropic effects. It is concluded that a large amount of MC-838 has slight cardiotonic properties which are not medi-ated via a beta-adrenergic mechanism.
