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Inhibition of Na + ‐K + pump activity by divalent cations in intact peritoneal mast cells of the rat
Author(s) -
Knudsen Trorben,
Berthelsen Henrik C.,
Johansen Torben
Publication year - 1990
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.1476-5381.1990.tb15827.x
Subject(s) - ouabain , divalent , chemistry , strontium , barium , calcium , lanthanum , magnesium , potassium , sodium , incubation , membrane transport , inorganic chemistry , radiochemistry , biophysics , membrane , biochemistry , biology , organic chemistry
1 The inhibition by the divalent cations magnesium, barium and strontium and the trivalent ion lanthanum of the Na + ‐K + pump in the plasma membrane of rat peritoneal mast cells was studied in pure mast cell populations by measurement of the ouabain‐sensitive uptake of the radioactive potassium analogue, 86 rubidium ( 86 Rb + ). 2 Exposure of the cells to magnesium induced a time‐ and concentration‐dependent decrease in the ouabain‐sensitive K + ( 86 Rb + )‐uptake of the cells without influencing the ouabain‐resistant uptake. The time‐dependent decrease was apparent after incubation of the cells for 10 min or more, but no decrease was observed after 2 min incubation when the cells are supposed to be loaded with sodium due to the cell isolation procedure. 3 Barium and strontium caused concentration‐dependent decreases in the ouabain‐sensitive K + ‐( 86 Rb + ) ‐uptake of the cells but the ouabain‐resistant uptake was not changed. Half maximum decrease in the ouabain‐sensitive K + ( 86 Rb + )‐uptake was observed with 1.8 m m magnesium, 1.2 m m barium and 0.7 m m strontium. 4 The trivalent ion lanthanum blocked almost completely the ouabain‐sensitive K + ( 86 Rb + )‐uptake at a concentration of 1 μ m as does 1 m m calcium. Combining either of these ions with magnesium had no further inhibitory effect on the ouabain‐sensitive uptake. 5 In conclusion, in addition to the previously suggested modulation by calcium of the activity of the Na + ‐K + pump, evidence is provided in this investigation that the modulation may be a more general effect of divalent and polyvalent cations present in the extracellular space through their influence on the sodium permeability of the plasma membrane.