THE INFLUENCE OF SODIUM-FREE SOLUTIONS ON THE MEMBRANE POTENTIAL OF FROG MUSCLE FIBERS.
The membrane potential of frog sartorius muscle fibers in a Cl- and Na-free Ringer's solution when sucrose replaces NaCl is about the same as that in normal Ringer's solution. The K(+) efflux is also about the same in the two solutions but muscles lose K and PO(4) in sucrose Ringer's solutions. The membrane potential in sucrose Ringer's solution is equal to that given by the Nernst equation for a K(+) electrode, when corrections are made for the activity coefficients for K(+) inside and outside the fiber. For a muscle in normal Ringer's solution, the measured membrane potential is within a few millivolts of E(K). This finding is incompatible with a 1:1 coupled Na-K pump. It is consistent with either no coupling of Na efflux to K influx, or a coupling ratio of 3 or greater.
D000818:Animals; D001001:Anura; D007477:Ions; D008564:Membrane Potentials; D009132:Muscles; D010827:Physiology; D011188:Potassium; D012106:Research; D012964:Sodium; D012965:Sodium Chloride; D012996:Solutions; D013395:Sucrose
D007477:Ions; D012996:Solutions; D012965:Sodium Chloride; D013395:Sucrose; D012964:Sodium; D011188:Potassium
EXPERIMENTAL LAB STUDY; MUSCLES; PHYSIOLOGY; SOLUTIONS