Fig. 6. Effect of hypercapnic acidosis and Na⁺/K⁺ ATPase-pump inhibition on intracellular Na⁺ levels. (A) Typical recording of [Na⁺]_i in the continued presence of 5 µmol l^–1 cariporide. Switching from a 5% to a 12% CO₂ buffered solution had no effect on Na⁺_i levels, whereas addition of the Na⁺/K⁺ ATPase pump inhibitor, ouabain at 10 µmol l^–1 during hypercapnic acidosis, substantially increased [Na⁺]_i. (B) Overall results showing mean sodium-binding benzofuran isophthalate (SBFI) fluorescence values, indicating the lack of effect of hypercapnic acidosis on Na⁺_i levels and the significant increase produced by ouabain. Values are means ± s.e.m., N=5 cells. *P<0.05 with respect to values before hypercapnia.