Measurement and control of intracellular magnesium ion concentration in guinea pig and ferret ventricular myocardium.
Intracellular magnesium and sodium ionic concentrations have been measured in mammalian ventricular myocardium using ion-selective micro-electrodes. The values for [Na+]i and [Mg2+]i are 9.5 +/- 0.3 and 2.4 +/- 0.2 mM, respectively. Increasing extracellular [Mg] or decreasing extracellular [Na] both caused a rise of [Mg2+]i and a fall of [Na+]i. Superfusion with ouabain caused a small rise of [Mg2+]i as well as a rise of [Na+]i. Reduction of extracellular [Mg] or cell depolarisation had no effect on [Mg2+]i. A possible hypothesis to explain these results is proposed, namely that the transmembrane Na+ and Mg2+ gradients are coupled such that an alteration of one gradient will affect the other. However, the relative stability of [Mg2+]i suggests that it is also affected by other factors, such as intracellular buffering of the ion.
D000818:Animals; D002301:Cardiac Glycosides / Q000494:pharmacology; D002335:Carnivora; D002463:Cell Membrane Permeability / Q000187:drug effects; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000032:analysis; D008274:Magnesium / Q000032:analysis* / Q000378:metabolism; D008839:Microelectrodes / Q000592:standards; D009206:Myocardium / Q000032:analysis* / Q000166:cytology; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000032:analysis / Q000378:metabolism
D002301:Cardiac Glycosides; D010042:Ouabain; D012964:Sodium; D008274:Magnesium