AJP - Renal Physiology, Vol 262, Issue 5 723-F730, Copyright © 1992 by American Physiological Society
Intracellular pH in OK cells. II. Effects of temperature on cell pH
M. Graber, C. Barry, J. Dipaola and A. Hasagawa
Veterans Affairs Medical Center, Northport, New York 11768.
Intracellular pH (pHi) is known to acidify as temperature rises. It has
been proposed that this relationship reflects the temperature dependence of
the dissociation constant of intracellular buffers. The purpose of this
study was to evaluate whether H+ production and membrane acid/base
transport events also contribute to the temperature dependence of pHi. This
relationship was studied by means of the 490/450-nm fluorescence of
2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, to measure pHi of OK cells
grown on cover slips and perfused in a thermostated chamber. As temperature
was increased from 12 degrees C, pHi progressively acidified, until a
precipitous and large alkalinization appeared at 40-45 degrees C. We
specifically examined the range from 25 to 37 degrees C, over which pHi
acidified by 0.32 units from 7.50 to 7.18. The three major components that
regulate pHi in the OK cell were quantitated as follows: H+ production, H+
extrusion via Na(+)-H+ antiport, and the passive H+ leak from buffer to
cell. Relative to the rate at 25 degrees C, acid production at 37 degrees C
increased by 129% (3.82 +/- 0.78 vs. 8.76 +/- 1.12 mmol.l-1.min-1). The
recovery of pHi after NH4Cl loading was used to measure the rate of
Na(+)-H+ antiport, and in Na(+)-free depolarized cells the magnitude of
passive H+ conductance through the leak pathway. Compared with the rate at
25 degrees C, at 37 degrees C the Na(+)-H+ antiport increased by 26% (1.25
+/- 0.22 vs. 1.58 +/- 0.25 mmol.l-1.min-1) and the H+ permeability
increased by 140% (0.005 +/- 0.001 vs. 0.012 +/- 0.003 cm/s).(ABSTRACT
TRUNCATED AT 250 WORDS)
