86Rb+ ion fluxes in resting and immunologically stimulated mucosal mast cells.
We studied fluxes of Rb+ ions, using its 86Rb isotope as a radioactive tracer in living rat mucosal mast cell cultures (RBL-2H3 line) grown to high density on beads. Continuously perfused samples of these cells could be immunologically stimulated by antigen clustering of IgE bound to the cells type I Fc epsilon receptors (Fc epsilon RI) and both the cellular response, as measured by the secreted mediators, as well as the uptake of 86Rb+ of the perfused sample could be monitored. The following results were obtained. (i) In resting cells, 86Rb+ influx is observed upon exposure to extracellular 86Rb+. It proceeds with a monoexponential time course (tau = 30.6 +/- 8 min) reaching a steady-state distribution of [86Rb+]int/[86Rb+]ext = 31.6 +/- 6.4 and can be inhibited by ouabain. (ii) Fc epsilon RI clustering-mediated stimulation of these cells causes an immediate and marked increase in both amplitude and rate of 86Rb+ uptake, which also fits a monoexponential function (tau = 26.8 +/- 8.6 min). (iii) This stimulated 86Rb+ uptake can also be inhibited by ouabain. It is not caused by Ca2+ influx or by the exocytotic process as evidenced by the fact that it is also observed in buffer to which no Ca2+ ions were added. Analysis of these results by a simple model taking into account unidirectional 86Rb+ influx by the Na+/K(+)-dependent ATPase and its efflux by K+ channels yields a resting cells unidirectional K+ uptake of 3.0 +/- 1.1 10(7) ions/cell/s, which is increased by ca. 10% upon clustering of the Fc epsilon RI by IgE and antigen. The stimulated influx is suggested to be due to enhanced activity of the Na+/K(+)-dependent ATPase, reflecting increased permeability for Na+ ions.
Pilatus
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Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
Pecht
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D000818:Animals; D002118:Calcium / Q000502:physiology; D002460:Cell Line; D002463:Cell Membrane Permeability; D005089:Exocytosis; D008407:Mast Cells / Q000276:immunology / Q000378:metabolism*; D008564:Membrane Potentials; D009092:Mucous Membrane / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology; D051381:Rats; D017455:Receptors, IgE / Q000502:physiology; D012414:Rubidium Radioisotopes / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology
D015221:Potassium Channels; D017455:Receptors, IgE; D012414:Rubidium Radioisotopes; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D002118:Calcium