title: Ouabain binding and potassium transport in young and old populations of human red cells.
abstract: Human red blood cells were separated according to density by centrifugation through mixtures of phthalate esters. The densest 20% of the erythrocyte population (old cells) had reduced volume and water content compared to the lightest 20% of the cells (young cells). Corpuscular hemoglobin content was unchanged. Young cells had 50% more potassium (K+) than old cells, but their total intracellular concentration was only slightly higher, old cells had a small increase in sodium (Na+) concentration. Active K+ transport of young cells was 37% higher than that of old cells. [3H] + Ouabain binding revealed that this difference was the result of more K+ pump sites on young cells, which bound 530 ouabain molecules per cell at 100% K+ pump inhibition, as compared to 400 for old cells; unseparated cells bound 450-500 molecules. The relative rates of ouabain binding were identical for the two cell types. Old cells exhibited a greater passive permeability to K+, having a rate coefficient for ouabain-insensitive K+ influx 1.8 times that of young cells. There is evidence to suggest that in the face of reduced pump activity this augmented K+ "leak" might enhance the osmotic stability of the old cells and function to lengthen their life span.
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D004905:Erythrocyte Aging; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D010042:Ouabain / Q000097:blood* / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D012964:Sodium / Q000097:blood
chemical_list: D010042:Ouabain; D012964:Sodium; D011188:Potassium