Volume-sensitive KCl co-transport and taurine fluxes in horse red blood cells.
Potassium (using 86Rb+ as a tracer), amino acid and taurine fluxes were measured in horse red blood cells (RBCs). No volume-sensitive component of alanine and glycine transport was observed, and although volume-sensitive taurine fluxes were observed in most animals, their absolute magnitudes were small. K+ fluxes, however, were shown to be particularly volume sensitive; they were stimulated by cell swelling and inhibited by cell shrinkage. Sizeable fluxes were present at normal cell volumes. The volume-sensitive K+ flux was Cl- dependent and was abolished by Cl- replacement with methylsulphate. The Cl(-)-dependent K+ fluxes in horse red blood cells were stimulated by lowering in external pH to 6.9 and by treatment with the sulphydryl-reacting agent, N-ethylmaleimide. They were inhibited by the potent K(+)-Cl- co-transport inhibitor, DIOA, ([(dihydroindenyl)oxy]alkanoic acid) but were insensitive to the Na(+)-K(+)-Cl- co-transport inhibitors, frusemide and bumetanide. A Cl- channel inhibitor, 5-nitro-2-(phenylpropyl-amino)-benzoate (NPPB), produced partial inhibition. These results suggest that regulatory volume decrease in horse red blood cells is achieved predominantly by volume-sensitive K+ efflux mediated via a K(+)-Cl- co-transport system with similar properties to those observed in the red blood cells of other species. The significance of these findings and their rheological consequences are discussed.
Gibson
J S
JS
Department of Veterinary Medicine, University of Cambridge.
Ellory
J C
JC
Culliford
S J
SJ
Fincham
D A
DA
D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002264:Carboxylic Acids / Q000494:pharmacology; D002352:Carrier Proteins / Q000032:analysis / Q000502:physiology*; D004911:Erythrocyte Volume / Q000502:physiology*; D004912:Erythrocytes / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D005033:Ethylmaleimide / Q000494:pharmacology; D005260:Female; D005665:Furosemide / Q000494:pharmacology; D006736:Horses / Q000097:blood*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007192:Indenes / Q000494:pharmacology; D008297:Male; D011188:Potassium / Q000378:metabolism; D027981:Symporters; D013654:Taurine / Q000378:metabolism*; D000096922:K Cl- Cotransporters
D002034:Bumetanide; D002264:Carboxylic Acids; D002352:Carrier Proteins; D005033:Ethylmaleimide; D005665:Furosemide; D007192:Indenes; D011188:Potassium; D027981:Symporters; D013654:Taurine; D000096922:K Cl- Cotransporters; C059990:((dihydroindenyl)oxy)alkanoic acid