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Properties of the Sodium Extrusion Mechanism Controlled by Nerve Growth Factor in Chick Embryo Dorsal Root Ganglionic Cells
Author(s) -
Skaper S. D.,
Varon S.
Publication year - 1980
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1980.tb11257.x
Subject(s) - nerve growth factor , incubation , extracellular , endocrinology , ouabain , medicine , sodium , chemistry , dinitrophenol , embryo , biophysics , biology , microbiology and biotechnology , biochemistry , receptor , organic chemistry
Cell dissociates from embryonic chick dorsal root ganglia, incubated for 6 h with 22 Na + , accumulated four to six times more radioactivity in the absence than in the presence of Nerve Growth Factor (NGF). The accumulation of radioactivity paralleled the external Na + concentration, indicating that the cells may have been reaching equilibrium with the medium. Delayed presentation of NGF to 22 Na + ‐loaded cells caused a rapid loss of radioactivity, even with extracellular 22 Na + still present, demonstrating that NGF caused an overall efflux of Na + rather than an accelerated equilibration. The Na + exclusion from 22 Na + ‐loaded cells was dependent upon NGF concentration. Use of nutrient‐rich medium, serum, and certain hormones and other proteins did not prevent the Na+ accumulation in the absence of NGF or its reversion by delayed NGF administration. Incubation of the ganglionic cells with ouabain or dinitrophenol during the 22 Na + loading period (no NGF) increased the rate, but not the magnitude, of loading. The same incubation carried out in a Na+‐free medium and followed by 22 Na + presentation resulted in fast radioactive loading that was identical to that occurring in drug‐free, NGF‐deprived cells and was not prevented by presentation of NGF together with the 22 Na + . These data are consistent with a model in which NGF acts through a Na + pump rather than by restricting Na+ influxes.