Evidence for a K(+)-H+ exchange in trout red blood cells.
AUTOR(ES)
Fievet, B
RESUMO
1. Exposure of trout red blood cells to beta-adrenergic agonist isoprenaline activates a cAMP-dependent Na(+)-H+ antiport, the movements of protons being compensated by a Cl(-)-OH- (or HCO3-) exchange mediated by band 3 protein. The absorption of water osmotically linked to sodium and chloride induces cell swelling. 2. In the presence of acetazolamide, anionic exchange is inhibited and activation of cationic exchange resulted in the first 2 min in a strong external acidification and a large internal alkalinization leading to a reversal of the transmembrane pH gradient. Then, for at least 1 h and despite the inhibition of Cl- entry, a net Na+ uptake occurred which was balanced by an equivalent K+ loss, with the result that cell volume and pH gradient remained unchanged. 3. In such conditions, the inactivation of the Na(+)-H+ exchanger by a beta-antagonist, propranolol, blocked Na+ entry while K+ continued to be lost. This volume-independent K+ efflux, which is thus independent of the Na(+)-H+ exchanger, was not accompanied by a Cl- efflux but was associated with large internal and external pH changes consistent with K(+)-H+ exchange. 4. The K+ loss and the related pH changes are inhibited by compounds which are known to inhibit the K(+)-anion co-transporter in trout red cells, i.e. 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (Dids) and niflumic acid.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1175317Documentos Relacionados
- Effects of anions on the Na(+)-H+ exchange of trout red blood cells.
- Volume-activated Cl(-)-independent and Cl(-)-dependent K+ pathways in trout red blood cells.
- Volume-activated DIDS-sensitive whole-cell chloride currents in trout red blood cells.
- Membrane sidedness and the interaction of H+ and K+ on Ca2(+)-activated K+ transport in human red blood cells.
- The effects of transport inhibitors on sodium outflux and influx in red blood cells: evidence for exchange diffusion