ATP-Dependent chloride influx into internally dialyzed squid giant axons

Measurements were made of 36C1 influx into squid giant axons whose internal solutes were controlled by means of internal dialysis. When the intracellular chloride concentration was 50mM and the internal concentration of adenosine 5'-triphosphate (ATP) was 4mM, the average chloride influx was 11.6 pmoles/cm2 x sec. When the axons were dialyzed with an ATP-free solution, the average influx fell to 5.1 pmoles/cm2 x sec. The effect was fully reversible upon the return of ATP to the dialysis fluid. Chloride-36 influx in the presence and absence of ATP was found to be inversely related to the internal chloride concentration.