The effects of oxygenation upon the Cl-dependent K flux pathway in equine red cells.
The effects of oxygen tension (PO2) upon the K influx pathways of equine red cells have been studied using 86Rb+ as congener for K. Equilibration of cells in 100% nitrogen led to a low and Cl-independent K flux. Change to an atmosphere of 100% air led to a rapid sixfold increase in K flux. The oxygen-activated flux was entirely Cl dependent and was maintained for up to 3 h. Oxygenation-evoked activation was dependent upon PO2 over the physiological range with little effect up to 70% saturation of haemoglobin with oxygen but significant effects between 70 and 100%. K flux at low PO2 was unaffected by acidification to pH 7 or by hypotonic cell swelling. By contrast, at high PO2 both manipulations caused a substantial increase in Cl-dependent K flux. N-Ethylmaleimide (NEM; 1 mM) caused a progressive activation of KCl cotransport in cells held under nitrogen. The protein phosphatase inhibitor, calyculin A (100 nM), applied during NEM-evoked activation caused a "clamping" of K influx at that level. This "clamped" activity was unaffected by subsequent oxygenation. We conclude that oxygenation exerts a primary control over cotransport activity and that acidification and cell swelling are secondary modulators. It appears that oxygenation-evoked activation of the Cl-dependent K flux involves a serine/threonine phosphorylation event. Regulating the PO2 of the solution before and during experiments is important in controlling the activity of the KCl cotransporter and cell volume.
Honess
N A
NA
Department of Environmental and Evolutionary Biology, University of Liverpool, PO Box 147, Liverpool L69 3BX, UK.
Gibson
J S
JS
Cossins
A R
AR
D000143:Acids / Q000494:pharmacology; D000818:Animals; D002712:Chlorides / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004911:Erythrocyte Volume; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D005260:Female; D006736:Horses / Q000097:blood*; D008297:Male; D008387:Marine Toxins; D010080:Oxazoles / Q000494:pharmacology; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D011188:Potassium / Q000097:blood*
D000143:Acids; D002712:Chlorides; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; C059041:calyculin A; D010749:Phosphoprotein Phosphatases; D005033:Ethylmaleimide; D011188:Potassium; D010100:Oxygen