Modulation of Gardos channel activity by oxidants and oxygen tension: effects of 1-chloro-2,4-dinitrobenzene and phenazine methosulphate.
We compare the effects of 1-chloro-2,4-dinitrobenzene (CDNB) and phenazine methosulphate (PMS) on Gardos channel activity in normal human red cells. Both stimulate channel activity, both are dependent on the presence of extracellular Ca2+, and neither is affected by inhibitors of protein (de)phosphorylation. Of the two, PMS has a considerably greater effect. In addition, a major difference is that whilst CDNB has a greater stimulatory effect in oxygenated cells, by contrast, PMS is more effective in deoxygenated cells. These actions are correlated with ca. 30% inhibition of the plasma membrane Ca2+ pump (PMCA) and an increased sensitivity of the Gardos channel to Ca2+ (EC50 falling to about 150 nM). These findings are important in understanding how oxidants alter red cell cation permeability and may be relevant to the abnormal permeability phenotype shown by deoxygenated sickle cells.
Gibson
John S
JS
Department of Clinical Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK. jsg1001@cam.ac.uk
Muzyamba
Morris C
MC
D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002463:Cell Membrane Permeability; D004137:Dinitrochlorobenzene / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D008773:Methylphenazonium Methosulfate / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology*; D010100:Oxygen / Q000494:pharmacology*; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000378:metabolism*
D004137:Dinitrochlorobenzene; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496923:KCNN4 protein, human; D016877:Oxidants; D024681:Potassium Channels, Calcium-Activated; D008773:Methylphenazonium Methosulfate; D000252:Calcium-Transporting ATPases; D010100:Oxygen; D002118:Calcium