The effects of sodium pump inhibition produced by exposure to the cardiac glycosides, ouabain or dihydroouabain, or by reduction in extracellular potassium to 1.0 mM, on contractile state and sodium-calcium exchange were studied in primary monolayer cultures of chick embryo ventricular cells. Ouabain, 10(-6)M, dihydroouabain, 5 X 10(-5)M, and extracellular potassium of 1.0 mM all induced simila...

We examined the effect of several nitric oxide (NO) donors, authentic NO gas, and L-arginine in isolated cat and rat papillary muscles. We did not observe significant inotropic effects in response to any NO donor (ie, SPM-5185, C87-3754, and S-nitroso-N-acetylpenicillamine [SNAP]) from 1 nmol/L to 100 mumol/L. Similarly, authentic NO, at concentrations far in excess of those that maximally dila...

We investigated the inotropic effect of SCH00013 (4, 5-dihydro-6-[1-[2-hydroxy-2-(4-cyanophenyl)ethyl]-1,2,5, 6-tetrahydropyrido-4-yl]pyridazin-3(2H)-one) on isolated dog and rabbit ventricular muscles and in indo-1 loaded rabbit ventricular cardiomyocytes. SCH00013 elicited a positive inotropic effect in a concentration-dependent manner (10(-6) to 10(-4) M) in both species in the presence of b...

The action of a novel cardiotonic agent N-hydroxy-5,6-dimethoxy-benzo[b]thiophene-2-carboximide hydrochloride (Org 30029) on intracellular aequorin light transients and isometric contractions was investigated in isolated canine ventricular trabeculae. The positive inotropic effect of Org 30029 (30 ,uM-3 mM) was consistently associated with prolongation of the duration of contraction and an incr...

OBJECTIVES Recently, we showed that some new synthetic compounds structurally related to cilostamide (4-(1,2-dihydro-2-oxoquinolin-6-hydroxy)- N-cyclohexyl-N-methylbutanamide), a selective phosphodiesterase 3 (PDE3) inhibitor, produce inotropic effect comparable to that of IBMX (3-isobutyl-1-methylxanthine), a non-selective PDE inhibitor, but with differential chronotropic effect. In this inves...

The effects of acetylcholine and nicotine on isometric tension, in the presence and absence of atropine, hexamethonium, and endogenous norepinephrine stores, were examined in isolated cat atria and papillary muscles. Acetylcholine exerted a negative inotropic effect, competitively inhibited by atropine, in atrial and papillary muscle; in higher concentrations in papillary muscles, it produced a...

Perfusion of isolated rat heart with L-methionine produced a positive inotropic effect that was temporally preceded, as well as accompanied, by an increase of methyl group incorporation into N-methylated phospholipids of the myocardium. Maximal increase in contractile force development was associated with maximal methyl group incorporation. Both parameters showed a dose-related dependence on me...

The action of a novel cardiotonic agent N-hydroxy-5,6-dimethoxy-benzo[b]thiophene-2-carboximide hydrochloride (Org 30029) on intracellular aequorin light transients and isometric contractions was investigated in isolated canine ventricular trabeculae. The positive inotropic effect of Org 30029 (30 ,uM-3 mM) was consistently associated with prolongation of the duration of contraction and an incr...

BACKGROUND Aging is associated with marked alterations in myocardial contraction and relaxation, whereas halogenated anesthetics depress myocardial contractility. However, their effects on aging myocardium are unknown. METHODS Mechanical variables of left ventricular papillary muscles from adult and senescent rats (29 degrees C; pH 7.40; Ca2+ 1.0 or 0.5 mM; stimulation frequency, 12 pulses/mi...

It has been well documented that matrine, a tetracyclo-quinolizindine alkaloid, possessed a positive inotropic effect. However, the underlying mechanisms at the cellular and ion channel levels have not been completely clarified. Therefore, the present study was designed to identify the cellular target and the mechanisms of inotropic effect of matrine. Guinea pig papillary muscles were used to s...