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Sodium‐potassium pump current in smooth muscle cells from mesenteric resistance arteries of the guinea‐pig
Author(s) -
Nakamura Yoshito,
Ohya Yusuke,
Abe Isao,
Fujishima Masatoshi
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.0203o.x
Subject(s) - ouabain , chemistry , membrane potential , sodium , potassium , pipette , reversal potential , biophysics , patch clamp , guinea pig , analytical chemistry (journal) , medicine , chromatography , biochemistry , biology , receptor , organic chemistry
1 The Na + ‐K + pump current was studied in smooth muscle cells from mesenteric resistance arteries of guinea‐pigs by the use of the perforated patch‐clamp technique in the presence of blockers for various ion channels and exchangers. 2 When the Na + concentration in the pipette solution ([Na + ] i ) was 50 mM, an increase in the extracellular K + concentration ([K + ] o ) from 0 to 10 mM caused an outward current. Both the removal of K + from the bath solution and the application of 10 μM ouabain abolished this current. Thus, this K + ‐induced and ouabain‐sensitive current was considered to be the Na + ‐K + pump current. 3 The amplitude of the Na + ‐K + pump current increased as the membrane potential was made more positive until around 0 mV, while the amplitude saturated at more positive potentials than 0 mV. 4 An increase in [K + ] o or [Na + ] i amplified the Na + ‐K + pump current. For [K + ] o , the binding constant ( K d ) was 1.6 ± 0.3 mM and the Hill coefficient ( n H ) was 1.1 ± 0.2 ( n = 6 ). For [Na + ] i , K d was 22 ± 5 mM and n H was 1.7 ± 0.5 ( n = 4–19 ). 5 The presence of various monovalent cations other than Na + in the bath solution also evoked the Na + ‐K + pump current. The order of potency was K + ≥ Rb + > Cs + ≫ Li + . 6 Ouabain inhibited the Na + ‐K + pump current in a dose‐dependent manner with a K d of 0.35 ± 0.03 μM and an n H of 1.2 ± 0.1 ( n = 6–8 ). 7 The Na + ‐K + pump current increased as temperature increased. The temperature coefficient ( Q 10 ; 26–36 °C) was 1.87 ( n = 9 ). 8 In summary the present study characterized for the first time the Na + ‐K + pump current in vascular smooth muscle cells by the use of the voltage‐clamp method. The use of this method should provide essential information for Na + ,K + ‐ATPase‐mediated changes in the cell functions of vascular smooth muscle cells.