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The electrogenic Na‐pump and spontaneous contraction of the hypokalemic rat duodenum
Author(s) -
Akaike N.,
Wakita Y.
Publication year - 1986
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 - 10.1111/j.1476-5381.1986.tb16262.x
Subject(s) - duodenum , ouabain , contraction (grammar) , endocrinology , medicine , chemistry , muscle contraction , hypokalemia , diaphragm pump , potassium , biophysics , sodium , biology , materials science , organic chemistry , micropump , nanotechnology
1 The effects of the electrogenic Na‐pump on spontaneous contraction in the isolated, longitudinal muscle of the duodenum of rats which had been on a potassium‐deficient diet for 7 weeks, have been investigated. Intracellular levels of Na + are increased by this diet. 2 The spontaneous contraction of the duodenal muscle was stopped, transiently, by 0.5 to 120 m m ‐K + Krebs solution. The period of decrease of tone and amplitude occurring immediately after adding K + was shortened when the external K + concentration ([K] o ) was increased from 0.5 to 120 m m . 3 The decrease in tone and amplitude induced by K + was abolished by exposure of the tissue to 0 m m [K] o , by exposure to a temperature below 14°C, and in the presence of ouabain (3 × 10 −5 ‐10 −4 m ). 4 The spontaneous contraction of ‘Na‐rich’ duodenum in bathing medium containing 15 m m K + and following inhibition of the electrogenic Na‐pump with cooling or ouabain was much the same as in the duodenum from rats fed balanced diets: i.e., increase of contractile tone immediately after adding K + . 5 To activate the Na‐pump in ‘Na‐rich’ duodenum, the external K + could be replaced by Rb + , Cs + , NH 4 + and Tl 3+ . The effectiveness was in the order K + > Rb + > Cs + > NH 4 + > Tl 3+ . 6 The possible existence of a neuronal or hormonal inhibitory mechanism affecting the active Na‐K transport in rat smooth muscle in situ , under conditions of hypokalemia, is discussed.