Inhibition of adrenergic proton extrusion in rainbow trout red cells by nitrite-induced methaemoglobinaemia.
The effects of nitrite-induced methaemoglobinaemia on adrenergic proton extrusion from rainbow trout red blood cells were studied using the pH-stat method. In control conditions adrenergic proton extrusion was completely inhibited by amiloride and was greater in deoxygenated than in oxygenated erythrocytes. Nitrite-induced methaemoglobinaemia was associated with a pronounced reduction in the catecholamine-stimulated proton efflux from both deoxygenated and oxygenated erythrocytes. In deoxygenated erythrocytes the initial proton efflux upon catecholamine stimulation decreased by 60-70%, while the percentage of methaemoglobin in the red cells increased from the control level of 1-3% to 20%. In oxygenated erythrocytes the decrease was 30% at the same methaemoglobin percentage range. It is suggested that the pronounced influence of nitrite-induced methaemoglobinaemia on adrenergic proton efflux results from an inhibition of the red cell sodium/proton exchanger by the R-like haemoglobin conformations.
Nikinmaa
M
M
Department of Zoology, University of Helsinki, Finland.
Jensen
F B
FB
D000818:Animals; D002352:Carrier Proteins / Q000097:blood; D004912:Erythrocytes / Q000378:metabolism*; D066298:In Vitro Techniques; D017136:Ion Transport; D008708:Methemoglobinemia / Q000097:blood* / Q000139:chemically induced; D011522:Protons; D011941:Receptors, Adrenergic / Q000378:metabolism; D012621:Seasons; D012977:Sodium Nitrite; D017923:Sodium-Hydrogen Exchangers; D014337:Trout / Q000097:blood*
D002352:Carrier Proteins; D011522:Protons; D011941:Receptors, Adrenergic; D017923:Sodium-Hydrogen Exchangers; D012977:Sodium Nitrite