Measurement of intracellular pH in isolated human detrusor smooth muscle cells.

Intracellular pH, pHi, was measured in isolated human detrusor smooth muscle cells by epifluorescence microscopy. The mean value was 7.07 +/- 0.19 when superfused with a CO2/HCO3- solution. Alteration of superfusate PCO2 also changed pHi whereas NaHCO3 changes were without effect, suggesting that the cell membrane is permeable to CO2 but impermeable to HCO3-. Nonbicarbonate H+ buffering power of the cell was calculated as 20.3 mequiv. x 1(-1) x pH unit-1. Addition of NH4Cl to the superfusate induced an alkalosis and, upon removal, a transient acidosis. The recovery from the acidosis allowed calculation of the acid extrusion rate from the cell. The rate was dependent on pHi and increased as the cell was more acid.