title: The influence of external sodium ions on the sodium pump in erythrocytes.
abstract: 1. A study has been made of the interaction between Na(+) and K(+) on the adenosine triphosphatase activity of erythrocyte ;ghosts', and on the K(+) influx and Na(+) efflux of intact erythrocytes. The adenosine triphosphatase activity and the ion movements were greater at a low external K(+) concentration in the absence of Na(+) than they were in the presence of 150mm-Na(+). The inhibition by external Na(+) of K(+) influx had an inhibitory constant of 5-10mm. 2. Activation by K(+) of kidney microsomal adenosine triphosphatase was retarded by Na(+), and activation by Na(+) was retarded by K(+). Fragmented erythrocyte membranes behaved similarly. 3. These observations suggest that there is competition between Na(+) and K(+) at the K(+)-sensitive site of the membrane.
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects*; D002462:Cell Membrane / Q000201:enzymology; D004912:Erythrocytes / Q000201:enzymology / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology*
chemical_list: D012964:Sodium; D000251:Adenosine Triphosphatases; D011188:Potassium