Fig. 2
From: Carbonic anhydrase IX is a pH-stat that sets an acidic tumour extracellular pH in vivo
Exofacial CA activity in HCT116 CA9 cells is in the physiological range of activity. a Exofacial pH transients measured with surface membrane-tagging WGA fluorescein in response to a 30 s pulse of 30 mM NH3/NH4 +-containing superfusate, measured in (i) intact HCT116 CA9 cells (n = 15) and (ii) intact HCT116 EV cells (n = 9), compared with paired runs in the presence of 100 µM ATZ, a broad-spectrum inhibitor of CA activity. (iii) Mean data for the peak and nadir of pHe transients in CA9 and EV cells, compared to the responses during ATZ inhibition. pH changes were smaller (i.e., better buffered) in CA9 cells, indicating membrane-bound CA activity. b CO2 hydration rates, normalised to protein concentration, measured in the cytoplasmic (C) and membrane (M) fractions of EV or CA9 HCT116 cells, compared to wild-type MDA-MB-468 cells, a cell line that naturally expresses CAIX in normoxia. Measurements performed on triplicate of independently harvested monolayers. Dashed line indicates spontaneous activity measured in buffer only (no cellular material). Red data points show values for each cell line after inhibition with 100 µM ATZ, showing reduction to spontaneous levels. Error bars are SEM. *indicates p<0.05 for the difference between C and M fractions and spontaneous activity in buffer alone (which is shown by the dashed line)
