AJP - Cell Physiology, Vol 258, Issue 3 C461-C469, Copyright © 1990 by American Physiological Society
Steady-state pHi, buffering power, and effect of CO2 in a smooth muscle-like cell line
R. W. Putnam and R. D. Grubbs
Department of Physiology and Biophysics, Wright State University School of Medicine, Dayton, Ohio 45401.
Intracellular pH (pHi) was studied in the smooth muscle-like cell line,
BC3H-1, using the pH-sensitive fluorescent dye
2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF). The initial pHi
measured in 20 mM Na N-2-hydroxyethylpiperazine-N'-2 ethanesulfonic
acid-buffered medium [NHB; external pH (pHo) 7.4, 37 degrees C] was 6.89
+/- 0.01 (n = 178). pHi was affected by changes in external pHo, pHi
changing by approximately 70% of the change in pHo. The intrinsic buffering
power (beta int) of these cells, measured either with NH4Cl or Na
propionate pulses, is low for muscle cells, averaging approximately 10
mM/pH unit. Steady-state pHi of BC3H-1 cells in NHB acidified reversibly on
exposure to 0.5 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS;
1.4 +/- 0.3 x 10(-4) pH/s), 1 mM amiloride (2.0 +/- 0.7 x 10(-4) pH/s), or
Na-free solution (8.3 +/- 2.4 x 10(-4) pH/s) and alkalinized upon exposure
to Cl-free solutions (9.7 +/- 2.2 x 10(-4) pH/s). Exposure of BC3H-1 cells
to CO2-HCO3-buffered solutions resulted in a transient acidification
followed by an alkalinization of 0.3-0.4 pH unit to a new steady-state pHi
of 7.27 +/- 0.01 (n = 65). This new steady-state pHi acidified very slowly
upon exposure to 1 mM amiloride (0.3 +/- 0.1 x 10(-4) pH/s), acidified more
rapidly upon exposure to 0.5 mM DIDS (5.9 +/- 0.6 x 10(-4) pH/s) or Na-free
solutions (9.8 +/- 1.0 x 10(-4) pH/s), and alkalinized on exposure to
Cl-free solutions (24.5 +/- 1.3 x 10(-4) pH/s).(ABSTRACT TRUNCATED AT 250
WORDS)
