Sodium-bicarbonate cotransport in retinal glial cells was studied in the ev
erted eyecup preparation of the rat. Intracellular pH was monitored with th
e indicator dye BCPCF and fluorescence confocal microscopy. Raising the Kconcentration from 3 to 12 mill in HCO3--buffered perfusate evoked an intra
cellular alkalinization in both astrocytes and Muller cells. The alkaliniza
tion developed more rapidly and was larger in astrocytes. The K+-induced al
kalinization was HCO3--dependent; it was reduced by 33% in astrocytes and 7
1% in Muller cells when HCO3- was removed from the perfusate. The alkaliniz
ation was effectively blocked by addition of 0.5 mM 4,4 "-diisothiocyanato-
stilbene-2,2'-disulfonic acid (DIDS). Removal of Na+ from the perfusate evo
ked a rapid acidification in both types of glial cells. The results indicat
e that astrocytes and Muller cells in situ in the rat retina possess an ele
ctrogenic Na+/HCO3- cotransporter. GLlA 26:302-308, 1999. (C) 1999 Wiley-Li
ss, Inc.