Studies on the lithium transport across the red cell membrane. I. Li+ uphill transport by the Na+-dependent Li+ counter-transport system of human erythrocytes.
Li+ net-transfer across cell membranes was studied on human erythrocytes and ghosts preloaded with 1-2 mM Li+ and incubated in saline media of varying composition at initial thermodynamic equilibrium for Li+. The following results were obtained: 1. Li+ is extruded from glycolyzing erythrocytes against an electrochemical gradient until a steady-state Li+ distribution is established after 24-28 h. 2. The initial rate of Li+ extrusion is not altered by ouabain or by reduction of ATP levels to less than 25% of the normal value. 3. Replacement of external Na+ by K+ or choline+ abolishes the establishment of an electrochemical Li+ gradient. 4. The Li+ distribution ratio Lie+/Lii+ increases proportional to the ratio Nae+/Nai+ at constant extravellular K+ concentrations. 5. In ghost suspension an uphill Li+ transport is driven by an oppositely directed Na+ gradient. The direction of the Li+ uphill transport can be reversed by reversing the Na+ gradient. From the results it is concluded that the Li+ uphill transport across human red cell membranes is mediated by a Na+-dependent Li+ counter-transport system. This system is not inhibited by ouabain and does not appear to be identical to the Na+-Na+ exchange system described by Garrahan and Glynn.
D000255:Adenosine Triphosphate / Q000378:metabolism; D001693:Biological Transport, Active; D002794:Choline / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D008094:Lithium / Q000097:blood*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*
D010042:Ouabain; D000255:Adenosine Triphosphate; D008094:Lithium; D012964:Sodium; D002794:Choline; D011188:Potassium