Electrochemical potentials of potassium in skeletal muscle under different metabolic states.
Intracellular potassium and membrane potential were measured simultaneously by means of double-barrelled liquid ion-exchange microelectrodes in single fibers of rat thigh muscle in vivo in rats maintained in seven different metabolic states. The K+ equilibrium potential (EK) was more negative than the simultaneously measured membrane potential (Em) in the normal state by 18.4 mV. K+ loading, acute and chronic, resulted in depolarization of Em due to increased serum K+ (hyperkalemia) with no increase in intracellular K+. K+ depletion resulted in hyperpolarization of Em as plasma K+ decreased proportionately more than intracellular K+. Low Na+ diet had no effect. Intracellular K+ was decreased in acute acidosis but not in the chronic state. Thus K+ depletion and acute acidosis are associated with intracellular K+ decrease. The fact that hyperpolarization exists in the former and not the latter is a reflection that hypokalemia accompanies the former condition. The hyperpolarizing states of K+ depletion and chronic acidosis are accompanied by decreased excitability and muscle weakness.
Khuri
R N
RN
Department of Medicine, School of Medicine, East Carolina University, Greenville, North Carolina 27858-4354.
Agulian
S K
SK
Abdulnour-Nakhoul
S
S
Nakhoul
N L
NL
D000818:Animals; D001158:Arteries; D001639:Bicarbonates / Q000097:blood; D002245:Carbon Dioxide / Q000097:blood; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D008839:Microelectrodes; D009132:Muscles / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D001639:Bicarbonates; D002245:Carbon Dioxide; D011188:Potassium