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Properties of the Na + /K + pump current in small neurons from adult rat dorsal root ganglia
Author(s) -
Hamada Kanako,
Matsuura Hiroshi,
Sanada Mitsuru,
Toyoda Futoshi,
OmatsuKanbe Mariko,
Kashiwagi Atsunori,
Yasuda Hitoshi
Publication year - 2003
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0705170
Subject(s) - pipette , chemistry , tetraethylammonium , membrane potential , diaphragm pump , dorsal root ganglion , biophysics , ouabain , voltage clamp , patch clamp , analytical chemistry (journal) , sodium , potassium , anatomy , dorsum , biochemistry , chromatography , materials science , biology , nanotechnology , receptor , organic chemistry , micropump
The present investigation was undertaken to characterize the Na + /K + pump current in small (25 μ m in soma diameter) dorsal root ganglion (DRG) neurons isolated from lumbar L4‐6 segments of adult rats. The Na + /K + pump current was identified as an ouabain‐sensitive current during square voltage steps to membrane potentials between +40 and −120 mV, using the whole‐cell patch‐clamp technique in which Ca 2+ and K + channel currents and Na + /Ca 2+ exchange currents were minimized. The Na + /K + pump current was practically time‐independent over the entire voltage range examined and exhibited a voltage‐dependence; its current – voltage ( I–V ) relationship displayed a positive slope at potentials between −120 and 0 mV but nearly plateau levels at positive membrane potentials. The concentration‐dependent block of Na + /K + pump current (activated by 30 m M pipette Na + ) by ouabain at concentrations between 0.1 μ M and 5 m M was biphasic and was well described using a two‐binding site model with dissociation constants for high‐ and low‐affinity binding sites of 0.20 and 140.1 μ M , respectively. The relative amplitude of the Na + /K + pump current produced by low‐ and high‐affinity sites (probably α 1 β 1 and α 3 β 1 isozymes, respectively) was estimated to be 13 : 1 in the presence of 30 m M Na + in the pipette solution. Additionally, the activation of Na + /K + pump current by pipette Na + at concentrations ranging from 5 to 100 m M also exhibited a biphasic concentration dependence which can be reasonably well fitted by assuming the existence of two isozymes having high and low affinities for Na + (6.7 and 67.6 m M , respectively). Thus, the present investigation provides functional evidence to suggest that the Na + /K + ATPase comprises two functionally distinct isozymes as expected for α 1 β 1 and α 3 β 1 in rat small DRG neurons.British Journal of Pharmacology (2003) 138 , 1517–1527. doi: 10.1038/sj.bjp.0705170