Starting pHi, reference pHi, and representative pHi tracings from pNBC1-transfected and untransfected HEK293 cells. A, B: Box and whisker diagram of the starting- and reference pHi values from pNBC1-transfected and untransfected cells. Steady-state pHi was significantly higher in transfected cells, pointing to increased baseline Na+/HCO3- cotransport activity (*: p < 0.001, Student's t-test for paired samples, n = 7). The reference pHi after acidification was, however, not different between the two. C: After imposing an acid load using the "NH4-prepulse" method, cells acidified to a similar extent. Upon Na+ readdition, most untransfected cells showed no significant recovery, while pHi increased rapidly in transfected cells (representative tracings). It should be noted that our 2-point calibration approach is optimized for the low pHi values at which transporter activity is measured, and that the higher pHi values are therefore overestimated.
Bachmann et al. BMC Cell Biology 2008 9:70 doi:10.1186/1471-2121-9-70