title: Effect of external ATP on the plasma membrane permeability and (Na+ +K+)-ATPase activity of mouse neuroblastoma cells.
abstract: 1. Addition of 3.5 mM ATP to mouse neuroblastoma Neuro-2A cells results in a selective enhancement of the plasma membrane permeability for Na+ relative to K+, as measured by cation flux measurements and electro-physiological techniques. 2. Addition of 3.5 mM ATP to Neuro-2A cells results in a 70% stimulation of the rate of active K+ -uptake by these cells, partly because of the enhanced plasma membrane permeability for Na+. Under these conditions the pumping activity of the Neuro-2A (Na+ +K+)-ATPase is optimally stimulated with respect to its various substrate ions. 3. External ATP significantly enhances the affinity of the Neuro-2A (Na+ +K+)-ATPase for ouabain, as measured by direct [3H]ouabain-binding studies and by inhibition studies of active K+ uptake. In the presence of 3.5 mM ATP and the absence of external K+ both techniques indicate an apparent dissociation constant for ouabain of 2 X 10(-6)M. Neuro-2A cells contain (3.5 +/- 0.7) X 10(5) ouabain-binding sites per cell, giving rise to an optimal pumping activity of (1.7 +/- 0.4) X 10(-20) mol K+/min per copy of (Na+ +K+)-ATPase at room temperature.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009447:Neuroblastoma; D010042:Ouabain / Q000378:metabolism; D011485:Protein Binding; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D010042:Ouabain; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase