title: Potasssium transport in human blood lymphocytes treated with phytohemagglutinin.
abstract: We have confirmed that phytohemagglutinin (PHA) rapidly enhances the uptake of potassium (K+) by human blood lymphocytes. PHA, however, did not produce an increase in lymphocyte K+ concentration. The apparent steady-state of cell K+ concentration despite the marked increase in uptake of 42K+ could be explained by either an increase in K+-K+ exchange or an increase in concentrative (active) K+ accumulation in association with an increase in the leak of K+ from the cell. We compared, therefore, the uptake of 42K+ with the decrement in cellular K+ content when active transport was inhibited by ouabain. These studies established that K+-K+ exchange was negligible in human blood lymphocytes and that the increase in 42K+ uptake after PHA treatment represented concentrative transport. Our studies did indicate that 42K+ exodus from PHA treated lymphocytes increased markedly from 19 to 38 mmol-1 cell water-1-h-1. Within the same time period K+ influx into PHA-treated lymphocytes increased from 20 to 38 mmol-1 cell water-1-h-1. Thus, PHA produces a marked increase in the permeability of the lymphocyte membrane to K+, and the increase in active K+ influx in PHA-treated lymphocytes may represent a homeostatic response by the membrane K+ transport system to the increase in K+ efflux. Increased K+ turnover was observed at the lowest concentrations of PHA which produced an observable increase in [3H]thymidine incorporation into DNA. Thus, PHA produces an increase in K+ permeability that closely parallels its mitogenic effect. The rapid increase in K+ influx preceding blastogenesis and mitogenesis is required, therefore, to maintain normal intracellular K+ concentration. An adequate intracellular K+ concentration is essential for the synthetic processes required for cell transformation or division.
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D001693:Biological Transport, Active / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D006801:Humans; D037102:Lectins / Q000494:pharmacology*; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D008433:Mathematics; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*
chemical_list: D037102:Lectins; D010042:Ouabain; D004247:DNA; D011188:Potassium