Biomaterial Database

Magnesium and intracellular sodium activity in cardiac Purkinje fibers. 1990

E Aceto, and M Vassalle

Department of Physiology, State University of New York, Brooklyn.

The actions of magnesium on intracellular sodium activity (aiNa), transmembrane potentials and contractile force were studied in sheep cardiac Purkinje fibers perfused in vitro. Increasing [Mg]o from 1.05 to 2-8 mM shortens the action potential, decreases force and increases aiNa in active (and quiescent) fibers. High Ca (8.1 mM) increases force and decreases aiNa: in its presence, 8 mM Mg ('high Mg') decreases force as well as the action potential duration and still increases aiNa. Manganese decreases force and aiNa: the effects of high Mg are not changed by Mn-induced blockade of the slow channel. Even in the presence of 0.25 mM lidocaine (which decreases action potential duration, force and aiNa), high Mg increases aiNa, has little effect on the action potential duration and increases the threshold requirements. In the absence of [Ca]o, 1.35 mM Sr increases the action potential duration as well as aiNa and reduces force: high Mg markedly decreases aiNa, force and action potential duration. Thus, Mg decreases the duration of the action potential (as Ca does) but (in contrast to Ca) decreases contractile force (possibly by acting on intracellular structures) and increases intracellular Na activity. These effects are not dependent on Ca or Na influx and show that the increase in aiNa by Mg is the net result of opposing actions.

UI	MeSH Term	Description	Entries
D008012	Lidocaine	A local anesthetic and cardiac depressant used as an antiarrhythmia agent. Its actions are more intense and its effects more prolonged than those of PROCAINE but its duration of action is shorter than that of BUPIVACAINE or PRILOCAINE.	Lignocaine,2-(Diethylamino)-N-(2,6-Dimethylphenyl)Acetamide,2-2EtN-2MePhAcN,Dalcaine,Lidocaine Carbonate,Lidocaine Carbonate (2:1),Lidocaine Hydrocarbonate,Lidocaine Hydrochloride,Lidocaine Monoacetate,Lidocaine Monohydrochloride,Lidocaine Monohydrochloride, Monohydrate,Lidocaine Sulfate (1:1),Octocaine,Xylesthesin,Xylocaine,Xylocitin,Xyloneural
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D008297	Male		Males
D008345	Manganese	A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009200	Myocardial Contraction	Contractile activity of the MYOCARDIUM.	Heart Contractility,Inotropism, Cardiac,Cardiac Inotropism,Cardiac Inotropisms,Contractilities, Heart,Contractility, Heart,Contraction, Myocardial,Contractions, Myocardial,Heart Contractilities,Inotropisms, Cardiac,Myocardial Contractions
D011690	Purkinje Fibers	Modified cardiac muscle fibers composing the terminal portion of the heart conduction system.	Purkinje Fiber,Fiber, Purkinje,Fibers, Purkinje
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D005260	Female		Females
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