Previous studies have shown that chronic hyperhomocysteinemia is associated with an adverse cardiac remodeling and heart failure. This study, which utilized coronary-perfused hearts and superfused papillary muscle, was designed to determine whether homocysteine acts acutely to alter cardiac contractile function. Left ventricular developed pressure was used as a measure of systolic function in t...

A mode of action of endothelin (ET) on spontaneous contractions was investigated in ring preparations of isolated bovine mesenteric lymphatics. ET-1 at concentrations between 10-10 and 10-9 M caused a dose-dependent increase in the frequency of spontaneous contractions. The specific ETA-receptor antagonist BQ-123 (5 × 10-7 M) caused a significant inhibition of the ET-1-induced positive chronotr...

Background. Although a-adrenergic receptors are present in both normal and failing human left ventricular myocardium and mediate a positive inotropic effect in several other species, it is not known whether stimulation of myocardial ca-adrenergic receptors exerts a positive inotropic effect or contributes to basal contractile state in vivo in humans. Methods and Results. We studied 15 patients ...

The effects of phenylephrine and methoxamine were studied on pacemaker activity in the sinoatrial node and on atrial and ventricular contractility in isolated, blood-perfused atrial and ventricular preparations of dogs. Each drug was administered directly into the cannulated sinus node artery of an isolated atrium or the anterior descending branch of the isolated left ventricle over a period of...

OBJECTIVE Angiotensin II (ANG II) has recently been reported to increase inotropy in adult rabbit myocytes by a mechanism of alkalinization and consequent increased myofilament sensitivity to calcium. Accordingly, we tested the hypothesis that ANG II would have a greater inotropic effect during ischemic conditions than it would during normoxia, since ischemia-induced intracellular acidosis cont...

Although angiotensin II (Ang II) plays an important role in heart disease associated with pump dysfunction, its direct effects on cardiac pump function remain controversial. We found that after Ang II infusion, the developed pressure and +dP/dt(max) in isolated Langendorff-perfused mouse hearts showed a complex temporal response, with a rapid transient decrease followed by an increase above bas...

Although angiotensin II (Ang II) plays an important role in heart disease associated with pump dysfunction, its direct effects on cardiac pump function remain controversial. We found that after Ang II infusion, the developed pressure and dP/dtmax in isolated Langendorff-perfused mouse hearts showed a complex temporal response, with a rapid transient decrease followed by an increase above baseli...

The contractile and biochemical effects of the divalent cation ionophore A23187 were studied in isolated perfused guinea pig and rat ventricles. A23187 increased both cyclic adenosine 3':5'monophosphate (cyclic AMP) and cyclic guanosine 3':5'-monophosphate (cyclic GMP) concentrations in guinea pig ventricles. Associated with these changes in nucleotide content were positive inotropic effects an...

The positive inotropic effects of catecholamines have been postulated to result from an increase in the intracellular level of cyclic AMP (adenosine 3',5'-monophosphate) produced by activation of adenyl cyclase. Although lack of an inotropic effect by exogenously administered cyclic AMP has cast doubt on this hypothesis, cardiac cells are not readily permeable to cyclic AMP. The N-2'-O-dibutyry...