The Journal of General Physiology, Vol 54, 33-52,
Copyright © 1969 by The Rockefeller University Press
Anion Permeability of Frog Skeletal Muscle
L. E. Moore 1
1 From the Department of Physiology, Duke University, Durham, North Carolina 27706.
Dr. Moore's present address is Department of Physiology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
Unidirectional chloride effluxes from small bundles of muscle fibers were measured under equilibrium conditions. It was found that chloride effluxes are described by the constant field theory with a chloride permeability constant, Pcl, which is independent of the chloride concentration and the membrane potential. The value of Pcl at neutral pH was found to be 5 x 10-6 cm/sec. Chloride movements were markedly depressed at low pH and increased at high pH. It is concluded that chloride fluxes are independent of each other over a wide pH range. The effect of nitrate on the chloride effluxes was measured. It was found that both external and internal nitrate alone reduced the chloride efflux with the external nitrate appearing more effective than internal nitrate due to the nonequilibrium nature of the experimental conditions. Under equilibrium conditions the reduction of the chloride efflux by nitrate was greater than the external nitrate effect, both of which were dependent on the relative proportion of nitrate in the bathing solution. These results are consistent with the hypothesis that the inhibition of the chloride movements by nitrate is essentially symmetrical with regard to the inside and outside surfaces of the muscle membranes. The relative action of nitrate on the chloride efflux was independent of the external pH despite marked changes in the absolute values of the fluxes measured.
Submitted on November 25, 1968
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