Regulatory volume decrease in lamprey erythrocytes: mechanisms of K+ and Cl- loss.
The nature of the swelling-activated K+ and Cl- transport pathways of lamprey (Lampetra fluviatilis) erythrocytes was studied. In isosmotic medium, unidirectional K+ and Cl- effluxes appear to be largely mediated by conductive pathways. Unidirectional Cl- efflux increased as a function of a decrease in medium osmolarity. The swelling-activated Cl- transport was inhibited by R(+)-[(2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inde n-5- yl)oxy]acetic acid (DIOA), furosemide, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). In contrast, moderate cell swelling did not increase unidirectional ouabain-insensitive K+ efflux. However, inhibition of transport by Ba2+ was markedly reduced. This suggests that the Ba(2+)-sensitive pathway that mediated most of the K+ efflux in isosmotic conditions was inhibited by cell swelling and a Ba(2+)-insensitive pathway was activated. DIOA had no effect on K+ efflux in isosmotic or hyposmotic medium. These data and the finding that substitution of NO3- or SCN- for Cl- had only a minor effect on the swelling-induced net extrusion of K+ and water indicate that the pathways for K+ and Cl-, activated by cell swelling, are conductive.
Virkki
L V
LV
Department of Biosciences, FIN-00014 University of Helsinki, Finland.
Nikinmaa
M
M
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D048429:Cell Size / Q000187:drug effects; D002712:Chlorides / Q000097:blood*; D004533:Egtazic Acid / Q000494:pharmacology; D004912:Erythrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D006016:Glycolates / Q000494:pharmacology; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D007798:Lampreys / Q000097:blood*; D009997:Osmotic Pressure / Q000187:drug effects; D011188:Potassium / Q000097:blood*; D013654:Taurine / Q000097:blood
D002712:Chlorides; D006016:Glycolates; D013654:Taurine; D001464:Barium; D000001:Calcimycin; D004533:Egtazic Acid; C015765:MK 473; D005665:Furosemide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium