Volume-activated Rb+ transport in astrocytes in culture.
The involvement of K+ on the volume regulatory process in astrocytes was investigated by characterizing the hyposmolarity-induced efflux of K+ using 86Rb as a tracer. About 70 and 30% of the intracellular content of 86Rb was released after reductions in osmolarity from 320 to 160 or 220 mosM, respectively, during the time in which cells exhibit a volume regulatory response subsequent to swelling. No significant increase in 86Rb efflux was observed with lower reductions in osmolarity. The 86Rb efflux was Ca2+ independent and insensitive to temperature. It was inhibited by furosemide but not by bumetanide and was unaffected when nitrate, but not gluconate, replaced intracellular Cl-. The efflux was markedly inhibited by quinidine and by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Quinidine also prevented the volume regulatory decrease of cells, and this effect was overcome when a large cation permeability was imposed by gramicidin. In isosmotic conditions 86Rb efflux was not activated by N-ethylmaleimide, but this drug strongly inhibited the hyposmolarity-activated release. These findings suggest that 86Rb efflux from astrocytes associated to cell swelling is not mediated by an electroneutral cotransporter and rather favor the implication of a conductive exit pathway that may be a Ca(2+)-independent K+ channel.
Sanchez-Olea
R
R
Institute of Cell Physiology, Universidad Nacional Autónoma de México, Mexico City.
Moran
J
J
Martinez
A
A
Pasantes-Morales
H
H
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D003470:Culture Media; D005033:Ethylmaleimide / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology; D005942:Gluconates / Q000494:pharmacology; D006096:Gramicidin / Q000494:pharmacology; D007038:Hypotonic Solutions; D007700:Kinetics; D009566:Nitrates / Q000494:pharmacology; D009994:Osmolar Concentration; D011802:Quinidine / Q000494:pharmacology; D051381:Rats; D012413:Rubidium / Q000378:metabolism*; D013696:Temperature
D002712:Chlorides; D003470:Culture Media; D005942:Gluconates; D007038:Hypotonic Solutions; D009566:Nitrates; D002034:Bumetanide; D006096:Gramicidin; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D005665:Furosemide; D011802:Quinidine; D012413:Rubidium; D005033:Ethylmaleimide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C030691:gluconic acid