Intracellular pH and membrane potassium conductance in rabbit distal colon.
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.
Duffey
M E
ME
Department of Physiology, School of Medicine, State University of New York, Buffalo 14214.
Devor
D C
DC
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001826:Body Fluids / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology*; D003106:Colon / Q000502:physiology*; D004553:Electric Conductivity; D004848:Epithelium / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000502:physiology*; D007424:Intracellular Fluid / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits
D001639:Bicarbonates; D011188:Potassium