Biomaterial Database

Ca2+ measurement with a Ca electrode: artifacts due to some cardiotropic drugs. 1988

G Berson

Laboratoire de Pharmacologie Cardiovasculaire, INSERM Unité 195, Faculté de Médecine, Clermont-Ferrand, France.

In order to validate D. M. Bers' method ((1982) Amer. J. Physiol. 242, C404-C408) for the determination of free [Ca] in ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid (EG-TA)-buffered Ca solution, six cardiotropic drugs were checked for their ability to interfere with Ca2+ measurements with a Ca electrode: verapamil, diltiazem, perhexiline, amrinone, bepridil, and diproteverine. Only amrinone, up to 10(-4) M, showed no effect. With the other compounds, from 5 x 10(-6) to 10(-4) M a gradual increase of the potential was observed. Negligible with 1 mM Ca2+ in the solution, the effects increased while free Ca decreased, regardless of the presence of EGTA. Similar observations were made using a K+ electrode. Relying on the results obtained by three different techniques, potentiometric study, spectrophotometric study, and binding of 45Ca on Chelex 100 resin, it was concluded that the effects of these drugs on the potential measured with an ion-specific electrode are artifacts which are not due to a release of Ca ions from the Ca-EGTA complex. When using Bers' method for the determination of free calcium, interfering drugs should be added to the solutions only after Ca2+ measurements with the Ca electrode.

UI	MeSH Term	Description	Entries
D011199	Potentiometry	Solution titration in which the end point is read from the electrode-potential variations with the concentrations of potential determining ions. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
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
D002316	Cardiotonic Agents	Agents that have a strengthening effect on the heart or that can increase cardiac output. They may be CARDIAC GLYCOSIDES; SYMPATHOMIMETICS; or other drugs. They are used after MYOCARDIAL INFARCT; CARDIAC SURGICAL PROCEDURES; in SHOCK; or in congestive heart failure (HEART FAILURE).	Cardiac Stimulant,Cardiac Stimulants,Cardioprotective Agent,Cardioprotective Agents,Cardiotonic,Cardiotonic Agent,Cardiotonic Drug,Inotropic Agents, Positive Cardiac,Myocardial Stimulant,Myocardial Stimulants,Cardiotonic Drugs,Cardiotonics,Agent, Cardioprotective,Agent, Cardiotonic,Drug, Cardiotonic,Stimulant, Cardiac,Stimulant, Myocardial
D004566	Electrodes	Electric conductors through which electric currents enter or leave a medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum.	Anode,Anode Materials,Cathode,Cathode Materials,Anode Material,Anodes,Cathode Material,Cathodes,Electrode,Material, Anode,Material, Cathode
D001667	Binding, Competitive	The interaction of two or more substrates or ligands with the same binding site. The displacement of one by the other is used in quantitative and selective affinity measurements.	Competitive Binding
D013053	Spectrophotometry	The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.