Figure 8.

Glutamine synthetase (GS) immunolabel in wild-type (WT) and proximal tubule (PT)-specific Na⁺-bicarbonate cotransporter, electrogenic, isoform 1 (NBCe1) deletion [PT-NBCe1-A/B knockout (KO)] kidneys on basal and acid-loading diets. Column 1 shows micrographs of the proximal convoluted tubule (PCT; top row), proximal straight tubule (PST) in the medullary ray (PST-MR; middle row), and PST in the outer stripe of the outer medulla (PST-OSOM; bottom row). PT segments were identified by the presence of an apical brush border on high-power observation. In WT mice on the basal diet, there was intermediate-intensity GS immunolabel throughout the PT. Column 2 shows representative micrographs from a PT-NBCe1-A/B KO kidney on the basal diet. GS immunolabel intensity was substantially greater in the PCT, PST-MR, and PST-OSOM of KO mice than in WT mice. Column 3 shows GS immunolabel in acid-loaded WT mice. GS immunolabel intensity was very low throughout the PT, including the PCT, PST-MR, and PST-OSOM. Column 4 shows findings in acid-loaded PT-NBCe1-A/B KO kidneys. GS immunolabel intensity was substantially greater than in acid-loaded WT mice in the PCT, PST-MR, and PST-OSOM, and it was not detectably different from that observed in KO mice on the basal diet. Immunolabel micrographs are representative of findings in n = 4 male (M)/4 female (F) mice for each genotype on the basal diet and 6M/6F WT mice and 4M/5F KO mice on the acid-loading diet. *PT segments.