AJP - Renal Physiology, Vol 254, Issue 1 95-104, Copyright © 1988 by American Physiological Society
Effect of changes in extracellular Cl on intracellular Cl activity in frog skin
K. Drewnowska and T. U. Biber
Department of Physiology and Biophysics, Medical College of Virginia, Richmond 23298.
Intracellular Cl activity was measured in isolated frog skin (Rana pipiens)
with double-barrel microelectrodes. The initial rate of Cl uptake was
measured in Cl-depleted cells on reexposure to Cl on apical or basolateral
side. In skins with high and low conductance, cell CL activity increased
1.33 and 0.14 mM/s with apical reexposure and 5.03 and 0.30 mM/s with
basolateral reexposure, respectively. The initial Cl uptake was reduced on
the apical side by 93% with 10(-3) M DIDS
(4,4'-diisothiocyanostilbene-2,2'-disulfonic acid) and on the basolateral
side by 99% with 10(-3) M SITS
(4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid) plus 10(-5) M
bumetanide. The initial rate of Cl loss was measured when Cl was removed
from the bath: addition of HCO3 to Cl- and HCO3-free solution caused an
acceleration of Cl loss in absence but not in presence of DIDS on apical
side. In contrast, Cl loss across the basolateral side was not enhanced by
HCO3. In conclusion, Na-transporting cells have a substantial Cl
permeability on both sides. HCO3-stimulated Cl loss provides evidence for
Cl-HCO3 exchange and permits localization of this process in apical cell
membranes of granular cells.
