AJP - Cell Physiology, Vol 258, Issue 2 C336-C343, Copyright © 1990 by American Physiological Society
Intracellular pH and membrane potassium conductance in rabbit distal colon
M. E. Duffey and D. C. Devor
Department of Physiology, School of Medicine, State University of New York, Buffalo 14214.
Intracellular pH (pHc) was measured in the short-circuited epithelium of
rabbit distal colon using H(+)-selective microelectrodes. pHc was 6.91 +/-
0.02 (SE) when the bath pH was 7.4. Intracellular HCO3- activity (acHCO3-)
was estimated from these measurements to be 8 +/- 0 mM. When we replaced
all Cl- in the tissue bathing solutions with the impermeant anion
gluconate, pHc rose to 7.44 +/- 0.08 and acHCO3- increased to 30 +/- 6 mM.
These results demonstrate that this tissue contains a Cl(-)-HCO3- exchange
mechanism. During the Cl- replacement the apical membrane electrical
potential difference hyperpolarized from -55 +/- 1 to -74 +/- 3 mV,
suggesting that membrane ionic conductance had changed. Elevation of either
the apical or basolateral membrane bathing solution K+ concentration
produced a greater depolarization of membrane potential during Cl-
replacement than when tissues were bathed in normal electrolyte solutions.
In additional experiments, pHc was raised by lowering the bath CO2
concentration while the bath Cl- concentration was kept normal. Under these
conditions, membrane potential hyperpolarized and was more sensitive to the
elevation of bath K+ concentration than when pHc was normal. These results
suggest that membrane K+ conductance in this tissue is increased by
intracellular alkalinization.
