Components of O2-uptake by excised frog nerve dependent upon externally supplied sodium ions.

The steady rate of oxygen uptake of excised frog nerves equilibrated in a solution having a very low concentration of sodium ions increases to a new high steady rate when equilibrated with a solution containing a high concentration of this ion. The increase is suppressed by ouabain, indicating participation of the sodium pump. Part of this sodium-activated increase in oxygen uptake is inhibited by tetrodotoxin, indicating that passive influx of sodium ions into axons is part of the total process. Thus, two pathways for passive sodium influx into axons are suggested by these experiments. Procedures known to increase the passive permeability of axons for sodium ions also increase this sodium-activated oxygen uptake. A mechanism is proposed to explain that part of the sodium-activated oxygen uptake that is inhibited by tetrodotoxin.