THE CONTROL OF THE MEMBRANE POTENTIAL OF MUSCLE FIBERS BY THE SODIUM PUMP.
Frog sartorius muscles were made Na-rich by immersion in K-free sulfate Ringer's solution in the cold. The muscles were then loaded with Na(24) and the extracellular space cleared of radioactivity. When such Na-rich muscles were transferred to lithium sulfate Ringer's solution at 20 degrees C, Na efflux was observed to increase with time, to reach a maximum about 15 minutes after the transfer of the muscles to Li(2)SO(4), and then to decline. The decline in efflux from these muscles was proportional to ([Na](i))(8) over a considerable range of [Na](i). The membrane potential of Na-rich muscles was about -48 mv in K-free sulfate Ringer's at 4 degrees C but changed to -76 mv in the same solution at 20 degrees C and to -98 mv in Li(2)SO(4) Ringer's at 20 degrees C. By contrast, muscles with a normal [Na](i) showed a fall in membrane potential when transferred from K-free sulfate Ringer's to Li(2)SO(4) Ringer's solution. The general conclusions from this study are (a) that Na extrusion is capable of generating an electrical potential, and (b) that increases in [Na](i) lead to reversible increases in P(Na) of muscle fibers.
D000818:Animals; D001001:Anura; D002463:Cell Membrane Permeability; D002712:Chlorides; D004594:Electrophysiology; D007477:Ions; D008094:Lithium; D018020:Lithium Compounds; D008564:Membrane Potentials; D009132:Muscles; D009995:Osmosis; D010600:Pharmacology; D011188:Potassium; D012106:Research; D012964:Sodium; D012975:Sodium Isotopes; D000254:Sodium-Potassium-Exchanging ATPase; D013431:Sulfates
D002712:Chlorides; D007477:Ions; D018020:Lithium Compounds; D012975:Sodium Isotopes; D013431:Sulfates; C054097:lithium sulfate; D008094:Lithium; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium
CELL MEMBRANE PERMEABILITY; CHLORIDES; ELECTROPHYSIOLOGY; EXPERIMENTAL LAB STUDY; FROGS; LITHIUM; MUSCLES; OSMOSIS; PHARMACOLOGY; POTASSIUM; SODIUM; SODIUM ISOTOPES; SULFATES