23Na nuclear magnetic resonance study of intracellular sodium in vascular endothelial cells.
23Na(+)-NMR was used to determine the intracellular mobility and cell membrane permeability of Na+ in porcine vascular endothelial cells. The cells were grown as monolayers onto microcarrier beads and perfused with a medium containing Dy(P3O10)2(7-) to shift the extracellular from the intracellular Na+ resonance. Using triple quantum coherence filtered NMR experiments and spin echoes, it was shown that not all intracellular Na+ ions are in the extreme narrowing limit. The triple quantum coherence filtered experiments resulted in an observed R2f = 2022 +/- 302 s-1 and R2s = 200 +/- 28 s-1. From spin-echo experiments we obtained R2f = 2200 +/- 355 s-1 and a R2s = 145 +/- 15 s-1. These values are similar to those found in other cell systems and indicate water-Na(+)-protein interactions. Using single quantum NMR, the Na+ permeability of the endothelial membrane was determined. To obtain the Na+ transcellular permeability coefficient the cells were treated with 50 microM ouabain in the perfusion medium. Ouabain inhibits the Na-K pump and caused the intracellular Na+ concentration to increase in time. The permeability coefficient was obtained from the time dependence of the intracellular Na+ concentration. Assuming a monolayer of rectangularly shaped cells, we obtained a value of P = 0.02.10-5 cm s-1.
Gruwel
M L
ML
Department of Physiology I, Heinrich Heine University Düsseldorf, Germany.
Alves
C
C
Schrader
J
J
D000818:Animals; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009761:Nystatin / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000737:chemistry* / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013552:Swine
D009761:Nystatin; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase