Properties of the Na+-K+ pump in human red cells with increased number of pump sites.
We studied the Na+/K+ pump in red cells from an obese human subject (MAJ) in which the number of pumps/cell was 10-20 times higher than normal. Through measurements of the kinetic properties of several modes of operation of the Na+/K+ pump we determined that the pumps in MAJ cells are kinetically normal. In the presence of adequate metabolic substrate the maximum rates of Na+ pumping and lactate production saturated at 60 and 12 nmol/1 cell per h, respectively. Under physiological conditions pump and "leak" Na+ fluxes were similar in MAJ and normal cells. Since internal Na+ was lower in MAJ than in normal cells (Nai+ approximately 2 and 8 mmol/1 cell, respectively), we conclude that the reduction in cell Na+ allows the Na+/K+ pump in MAJ cells to operate at lower fraction of maximum capacity and to compensate for the increased number of pumps.
D000255:Adenosine Triphosphate / Q000097:blood; D002414:Cations, Monovalent; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D009765:Obesity / Q000097:blood*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood* / Q000494:pharmacology; D012964:Sodium / Q000097:blood*; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood
D002414:Cations, Monovalent; D007473:Ion Channels; D007773:Lactates; D019344:Lactic Acid; D010042:Ouabain; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium