pH-dependent modulation of intracellular free magnesium ions with ion-selective electrodes in papillary muscle of guinea pig.
A change in pH can alter the intracellular concentration of electrolytes such as intracellular Ca2+and Na2+ ([Na+]i) that are important for the cardiac function. For the determination of the role of pH in the cardiac magnesium homeostasis, the intracellular Mg2+ concentration ([Mg2+]i), membrane potential and contraction in the papillary muscle of guinea pigs using ion-selective electrodes changing extracellular pH ([pH]o) or intracellular pH ([pH]i) were measured in this study. A high CO2-induced low [pH]o causes a significant increase in the [Mg2+]i and [Na+]i, which was accompanied by a decrease in the membrane potential and twitch force. The high [pH]o had the opposite effect. These effects were reversible in both the beating and quiescent muscles. The low [pH]o-induced increase in [Mg2+]i occurred in the absence of [Mg2+]o. The [Mg2+]i was increased by the low [pH]i induced by propionate. The [Mg2+]i was increased by the low [pH]i induced by NH4Cl-prepulse and decreased by the recovery of [pH]i induced by the removal of NH4Cl. These results suggest that the pH can modulate [Mg2+]i with a reverse relationship in heart, probably by affecting the intracellular Mg2+ homeostasis, but not by Mg2+ transport across the sarcolemma.
Kim
Shang-Jin
SJ
Department of Pharmacology & Toxicology, College of Veterinary Medicine, Chonbuk National University, Jeonju 561-756, Korea.
Cho
In-Gook
IG
Kang
Hyung-Sub
HS
Kim
Jin-Shang
JS
D000818:Animals; D002413:Cations, Divalent; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D017136:Ion Transport / Q000502:physiology; D017736:Ion-Selective Electrodes / Q000662:veterinary; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D010210:Papillary Muscles / Q000378:metabolism*; D011422:Propionates / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*
D002413:Cations, Divalent; D011422:Propionates; D012964:Sodium; D008274:Magnesium