Intracellular pH and buffering power measured in isolated single cells from pregnant rat uterus

Intracellular pH (pHi) affects smooth muscle function yet there have been few direct pHi measurements. Using the fluorescent indicator, 2',7'-bis-2-(carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester, we report here the first measurements of pHi and buffering power (beta) in single, isolated, uterine smooth muscle cells. Mean pHi in cells from pregnant rat uteri was 7.09 +/- 0.08 (+/- S.E.M., n = 16 cells; 37 degrees C), and beta was found to be 12.8 +/- 2.8 mmol/l per pH unit (n = 15). The cells were able to regulate their pHi in the presence of butyrate when perfused in nominally CO2-free solution.