Defining the volume dependence of multiple K flux pathways of trout red blood cells.
The volume sensitivity of different K flux pathways has been determined in trout red blood cells subjected to volume perturbation. Gentle hyposmotic swelling induced a K influx in a Cl-containing saline but not in NO3- or methanesulfonate (MeSF)-containing salines, consistent with the activation of a Cl-dependent flux. Extreme hyposmotic swelling led to larger K fluxes in all salines but with reduced anion discrimination of the Cl-dependent flux. In contrast to these graded responses, isosmotic swelling using ammonium chloride or beta-adrenergic stimulation activated only Cl-dependent fluxes in an all-or-none fashion. The relationship between the hyposmotically and isosmotically induced pathways was studied by coactivation using either ammonium chloride or isoproterenol with anisosmotic treatment. Cells in ammonium chloride-containing hyposmotic salines showed no additive K flux over that induced by hyposmotic treatment alone, indicating that the isosmotically induced Cl-dependent flux was identical to the hyposmotically induced Cl-dependent flux. However, cells coactivated by hyposmotic and beta-adrenergic treatment showed a small Cl-dependent flux in addition to that induced by hyposmotic treatment alone. This small third component was unaffected by anisosmotic treatment. We conclude that the major Cl-dependent and Cl-independent K flux pathways are distinct and separate and that the former has an anion dependence that varies with cell volume and a volume sensitivity that varies with ionic strength.
Berenbrink
M
M
Integrative Physiology Research Group, School of Biological Science, University of Liverpool, United Kingdom.
Weaver
Y R
YR
Cossins
A R
AR
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D008387:Marine Toxins; D017686:Oncorhynchus mykiss / Q000097:blood*; D009995:Osmosis; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D011188:Potassium / Q000097:blood*
D000318:Adrenergic beta-Agonists; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D000643:Ammonium Chloride; C059041:calyculin A; D010749:Phosphoprotein Phosphatases; D007545:Isoproterenol; D011188:Potassium