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- Title
Properties of the Na+/K+ pump current in small neurons from adult rat dorsal root ganglia.
- Authors
Hamada, Kanako; Matsuura, Hiroshi; Sanada, Mitsuru; Toyoda, Futoshi; Omatsu-Kanbe, Mariko; Kasiwagi, Atsunori; Yasuda, Hitoshi
- Abstract
1 The present investigation was undertaken to characterize the Na[SUP+]/K[SUP+] pump current in small (⩽25 μm in some diameter) dorsal root ganglion (DRG) neurons isolated from lumbar L4-6 segments of adult rats. 2 The Na[SUP+]/K[SUP+] pump current was identified as an ouabain-sensitive current during square voltage steps to membrane potentials between +40 and -120mV, using the whole-cell patch-clamp technique in which Ca[SUP2+] and K[SUP+] channel currents and Na[SUP+]/Ca[SUP2+] exchange currents were minimized. The Na[SUP+]/K[SUP+] 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 0mV but nearly plateau levels at positive membrane potentials. 3 The concentration-dependent block of Na[SUP+]/K[SUP+] pump current (activated by 30 mM pipette Na[SUP+]) by ouabain at concentrations between 0.1 μM and 5 mM 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 μM, respectively. The relative amplitude of the Na[SUP+]/K[SUP+] pump current produced by low- and high-affinity sites (probably α1β1 and &alpha3β1 isozymes, respectively) was estimated to be 13:1 in presence of 30 mM (Na[SUP+] in the pipette solution. 4 Additionally, the activation of Na[SUP+]/K[SUP+] pump current by pipette Na[SUP+] at concentrations ranging from 5 to 100 mM also exhibited a biphasic concentration dependence which can be reasonably well fited by assuming the existence of two isozymes having high and low affinities for Na[SUP+] (6.7 and 67.6mM, respectively). 5 Thus, the present investigation provides functional evidence to suggest that the Na[SUP+]/K[SUP+] ATPase comprises two functionally distinct isozymes as expected for α3&beta1 in rat small DRG neutrons.
- Subjects
SENSORY ganglia; SODIUM channels; POTASSIUM channels; RATS
- Publication
British Journal of Pharmacology, 2003, Vol 138, Issue 8, p1517
- ISSN
0007-1188
- Publication type
Article
- DOI
10.1038/sj.bjp.0705170