Serum stimulation of sodium transport in human fibroblasts containing low and high levels of intracellular sodium |
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Authors: | Gillian Spurlock Kevin Morgan M Afzal Mir |
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Institution: | (1) Department of Medicine, Metabolism and Diabetes Unit, University of Wales College of Medicine, Heath Park, Cardiff, Wales |
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Abstract: | Summary The relationships between intracellular sodium content, sodium transport and serum effects were investigated in human fibroblasts. In the cells with low intracellular sodium (Na
iL
/+
;0.04 mol sodium/mg protein) serum stimulated the sodium-potassium pump as measured by ouabain-sensitive sodium efflux and rubidium influx and also exerted a transstimulation of ouabain-insensitive sodium transport resulting in net influx. In cells with high intracellular sodium (Na
iH
/+
;0.42 mol sodium/mg protein) all aspects of sodium transport were increased compared to Na
iL
/+
cells. In these cells serum caused no change in sodium-potassium pump activity but significantly increased the ouabain-insensitive sodium fluxes resulting in net efflux. In Na
iL
/+
cells, serum promoted net sodium influx through an amiloride-sensitive pathway that was undetectable in the basal state. In Na
iH
/+
cells the serum-stimulated net efflux was amiloride sensitive but this pathway also contributed to a major portion of sodium transport in the basal state. This study demonstrated that sodium-potassium pump activity is directed by the supply of internal sodium and that serum can increase this supply by promoting net influx, and that serum-induced sodium transport can be modified by intracellular sodium content. |
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Keywords: | sodium transport serum stimulation fibroblasts |
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