Volume-dependent K+ and Cl- fluxes in rat thymocytes.
1. Hypotonic stress unmasked inward and outward K+ and Cl- movements in rat thymocytes. This KCl flux stimulation was reduced by DIOA (dihydroindenyl-oxy-alkanoic acid), but not by DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonate), quinidine, DPAC 144 (5-nitro-2-(2-phenylethyl-amino)-benzoic acid), bumetanide or ouabain. 2. In isotonic media (308 +/- 5 mosmol kg-1), the cells exhibited the following DIOA-sensitive fluxes: (i) a K+ efflux of 42.7 +/- 17.1 mmol (l cells.h)-1 (mean +/- S.D., n = 7), (ii) a Cl- efflux of 68 +/- 21 mmol (l cells.h)-1 (n = 3), (iii) a Rb+ influx of 9.7 +/- 3.9 mmol (l cells.h)-1 (n = 6) and (iv) a Cl- influx of 9.4 +/- 4.1 mmol (l cells.h)-1 (n = 6). 3. Hypotonic shock (183-200 mosmol kg-1) induced a sevenfold stimulation of DIOA-sensitive K+ and Cl- effluxes and a twofold stimulation of DIOA-sensitive Rb+ and Cl- influxes (with a Rb+ to Cl- stoichiometry of 1.04 +/- 0.31; mean +/- S.D., n = 6). 4. The DIOA-sensitive membrane carrier catalysed net outward KCl extrusion (the outward/inward flux ratio was 5-7 in isotonic media and 20 in hypotonic media at 189 mosmol kg-1). Inhibition of DIOA-sensitive 36Cl- efflux by cell K+ depletion suggested coupling of outward K+ and Cl- fluxes. Conversely, inward K+ and Cl- fluxes were found to be uncoupled in NO3- media and in K(+)-free media. 5. The results clearly show that rat thymocyte membranes possess a 1:1 K(+)-Cl- co-transport system which is strongly activated by hypotonic shock and catalyses net KCl extrusion.
Soler
A
A
INSERM U2, Faculté de Médecine, Créteil, France.
Rota
R
R
Hannaert
P
P
Cragoe
E J
EJ
Garay
R P
RP
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002264:Carboxylic Acids / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D002713:Chlorine; D003600:Cytosol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007038:Hypotonic Solutions; D066298:In Vitro Techniques; D007192:Indenes / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011868:Radioisotopes; D051381:Rats; D017208:Rats, Wistar; D012413:Rubidium / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
C059990:((dihydroindenyl)oxy)alkanoic acid; D002264:Carboxylic Acids; D002712:Chlorides; D007038:Hypotonic Solutions; D007192:Indenes; D015221:Potassium Channels; D011868:Radioisotopes; D002713:Chlorine; D012413:Rubidium; D011188:Potassium; D002118:Calcium