title: ACTIVE Na+-, Cl-- AND HCO3--DEPENDENT ACID EXTRUSION IN ATLANTIC COD RED BLOOD CELLS IN WINTER ACTIVATED BY HYPERCAPNIA
abstract: The relationship between intracellular pH (pHi) and extracellular pH (pHe) was investigated in red blood cells from the Atlantic cod (Gadus morhua) in carbon dioxide/bicarbonate-buffered salines. In summer animals (August/September), similar transmembrane distribution ratios of chloride ([Cl-]i/[Cl-]e=rCl-) and protons ([H+]e/[H+]i=rH+) suggested a passive Donnan distribution of these ions across the red blood cell membrane at pHe 6.7&shy;8.4. In winter animals (February/March), a marked discrepancy occurred between rH+ and rCl- at low pHe values. The pronounced increase in rH+ resulted in significantly higher pHi values compared with those of red blood cells from summer animals and at pHe 6.7 pHi exceeded pHe by 0.3 units. The increases in rH+ values were completely abolished by cyanide and 2,4-dinitrophenol. The high disequilibrium rH+ values were sodium-, chloride- and bicarbonate-dependent. During hypercapnic acidosis, proton equivalents were extruded from the red blood cell. The resulting high rH+ values were accompanied by a reduced chloride shift into the red blood cell and a ouabain-insensitive net sodium influx. The net sodium influx into red blood cells from winter animals was significantly reduced in the presence of DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid). The results suggest the activation of a Na+-dependent Cl-/HCO3-exchanger at low pHe in the red blood cells of the Atlantic cod in winter.
authors.initials: M
authors.lastname: Berenbrink
authors.initials: C
authors.lastname: Bridges