If muscle membrane potentials vary as a function of ionic composition of the extracellular solution, changes in [K+]o should alter VM values. Moreover, EK, given by the Nernst equation, should accurately predict changing VM values. As extracellular potassium concentration is systematically increased, membrane voltage should be rendered more positive (less negative). Indeed, if [K+]i is 140 mM
(according to Bernstein’s model), extracellular [K+] much smaller than 140 mM (e.g., 5.4 mM, 10 mM) should elicit a large efflux of potassium ions, as reflected in the first two EK values listed in Table 1. As extracellular [K+] nears 140 mM, the strength of the outward potassium current should decrease, as reflected in the increasingly less negative EK values presented in Table 1. (Less …show more content…
Similarly, Bilbrey et al. (1973) note that the Goldman-Hodgkin-Katz equation more accurately predicts membrane potential as compared to the Nernst equation. Though the membrane functions principally as a potassium electrode, the Nernst equation does not account for the slight, but significant, permeability of the membrane to sodium ions (Bilbrey et al. 1973, 3011). In their study of the effects of potassium deficiency on skeletal muscle membrane function, the authors conclude that, membrane potential is indeed predictable by the GHK equation, even in rats with severe potassium depletion (3016).
Taken together, these studies suggest that the ratio of intracellular to extracellular potassium concentrations is the main determinant of membrane potential. However, because the Nernst function does not adjust for membrane permeability to other (e.g., sodium and chlorine) ions, the GHK seems to be the better predictor of membrane potential.
Replications of the present study, then, should employ a one-sample t-test that compares mean observed membrane voltages to EM values as predicted by the GHK equation. The resulting curve fit in
Figure 1 would thus be appended with the GHK
(according to Bernstein’s model), extracellular [K+] much smaller than 140 mM (e.g., 5.4 mM, 10 mM) should elicit a large efflux of potassium ions, as reflected in the first two EK values listed in Table 1. As extracellular [K+] nears 140 mM, the strength of the outward potassium current should decrease, as reflected in the increasingly less negative EK values presented in Table 1. (Less …show more content…
Similarly, Bilbrey et al. (1973) note that the Goldman-Hodgkin-Katz equation more accurately predicts membrane potential as compared to the Nernst equation. Though the membrane functions principally as a potassium electrode, the Nernst equation does not account for the slight, but significant, permeability of the membrane to sodium ions (Bilbrey et al. 1973, 3011). In their study of the effects of potassium deficiency on skeletal muscle membrane function, the authors conclude that, membrane potential is indeed predictable by the GHK equation, even in rats with severe potassium depletion (3016).
Taken together, these studies suggest that the ratio of intracellular to extracellular potassium concentrations is the main determinant of membrane potential. However, because the Nernst function does not adjust for membrane permeability to other (e.g., sodium and chlorine) ions, the GHK seems to be the better predictor of membrane potential.
Replications of the present study, then, should employ a one-sample t-test that compares mean observed membrane voltages to EM values as predicted by the GHK equation. The resulting curve fit in
Figure 1 would thus be appended with the GHK