Biomaterial Database

Effect of ambasilide, a new class III agent, on plateau currents in isolated guinea pig ventricular myocytes: block of delayed outward potassium current. 1992

Z H Zhang, and C H Follmer, and J S Sarma, and F Chen, and B N Singh

Department of Cardiology, Wadsworth Veterans Administration Medical Center, Los Angeles, CA.

The actions of ambasilide (LU-47110) on the action potential and membrane currents of isolated guinea pig ventricular myocytes were studied using voltage clamp techniques. Ambasilide (1 microM) prolonged the action potential (APD) at 20, 50 and 90% repolarization by 11.2 +/- 4.3, 13.8 +/- 3.9 and 13.6 +/- 3.7%, respectively, compared to control (n = 10). APD prolongation was attributed to the block of delayed rectifier outward current (Ik) in a concentration-dependent fashion (0.01-10 microM). The effects on the APD and Ik were both partially reversed after perfusion with drug-free Tyrode's solution. The block of Ik by ambasilide was compared to that by E-4031 (5 microM), a putative selective blocker of that fast, inwardly rectifying component of Ik identified in guinea pig ventricle. E-4031 produced about 65% block of Ik for pulse durations between 80 and 420 msec, but the block decreased as the pulse duration increased further, the block accounting for 34 +/- 5% of Ik at 6.3 sec. In contrast, the percentage of reduction of Ik by 10 microM ambasilide did not produce a consistent magnitude of block over a similar range of short depolarizations, but rather progressively decreased Ik as the pusle duration lengthened. Block at the end of a 2-sec pulse was about 48 +/- 8%, more block than could be attributed to an E-4031-sensitive current block alone. Whereas E-4031 (5 microM) shifted the activation curve of Ik 10 mV toward positive potentials and decreased the slope factor, k, by about 4 mV, ambasilide (5 microM) had no effect on these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D006352	Heart Ventricles	The lower right and left chambers of the heart. The right ventricle pumps venous BLOOD into the LUNGS and the left ventricle pumps oxygenated blood into the systemic arterial circulation.	Cardiac Ventricle,Cardiac Ventricles,Heart Ventricle,Left Ventricle,Right Ventricle,Left Ventricles,Right Ventricles,Ventricle, Cardiac,Ventricle, Heart,Ventricle, Left,Ventricle, Right,Ventricles, Cardiac,Ventricles, Heart,Ventricles, Left,Ventricles, Right
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D000889	Anti-Arrhythmia Agents	Agents used for the treatment or prevention of cardiac arrhythmias. They may affect the polarization-repolarization phase of the action potential, its excitability or refractoriness, or impulse conduction or membrane responsiveness within cardiac fibers. Anti-arrhythmia agents are often classed into four main groups according to their mechanism of action: sodium channel blockade, beta-adrenergic blockade, repolarization prolongation, or calcium channel blockade.	Anti-Arrhythmia Agent,Anti-Arrhythmia Drug,Anti-Arrhythmic,Antiarrhythmia Agent,Antiarrhythmia Drug,Antiarrhythmic Drug,Antifibrillatory Agent,Antifibrillatory Agents,Cardiac Depressant,Cardiac Depressants,Myocardial Depressant,Myocardial Depressants,Anti-Arrhythmia Drugs,Anti-Arrhythmics,Antiarrhythmia Agents,Antiarrhythmia Drugs,Antiarrhythmic Drugs,Agent, Anti-Arrhythmia,Agent, Antiarrhythmia,Agent, Antifibrillatory,Agents, Anti-Arrhythmia,Agents, Antiarrhythmia,Agents, Antifibrillatory,Anti Arrhythmia Agent,Anti Arrhythmia Agents,Anti Arrhythmia Drug,Anti Arrhythmia Drugs,Anti Arrhythmic,Anti Arrhythmics,Depressant, Cardiac,Depressant, Myocardial,Depressants, Cardiac,Depressants, Myocardial,Drug, Anti-Arrhythmia,Drug, Antiarrhythmia,Drug, Antiarrhythmic,Drugs, Anti-Arrhythmia,Drugs, Antiarrhythmia,Drugs, Antiarrhythmic
D001643	Bridged Bicyclo Compounds	Saturated alicyclic hydrocarbon molecules consisting of two rings that have two non-adjacent atoms in common.	Bicyclo Compounds,Bicyclo Compounds, Bridged
D062365	Aminobenzoates	Derivatives of BENZOIC ACID that contain one or more amino groups attached to the benzene ring structure. Included under this heading are a broad variety of acid forms, salts, esters, and amides that include the aminobenzoate structure.	Aminobenzoic Acids,Acids, Aminobenzoic