AbstractIn the absence of external HCO3, resting membrane potentials (Vm) in extensor digitorum longus muscle were depolarized as compared to the normal Vm in the presence of HCO3. Removal of Na or Cl from the HCO3‐free media induced repolarization. In muscle in HCO3buffer at 20°C, internal K, Na, and Cl activities were analyzed with liquid ion selective microelectrodes. The averages were respectively, 119.7 ± 2.1, 6.69 ± 0.3, and 3.41 ± 0.06 mM. In a high proportion of cells analyzed, the equilibrium potential for Cl was negative to Vm. Removing external HCO3, decreased internal K while internal Na and Cl increased. An increase in temperature and the application of HCO3significantly lowered internal activities of both Na and Cl. Removal of HCO3with temperature held constant caused a rapid depolarization, an increase in internal Na and Cl, and a decrease in internal K. Furosemide (10 μM) induced a repolarization of cells that were previously depolarized in the HCO3‐free state, but the drug does not decrease int
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