The Journal of General Physiology, Vol 89, 541-562, Copyright © 1987 by The Rockefeller University Press
Characterization of the basolateral membrane conductance of Necturus urinary bladder
JR Demarest and AL Finn
Necturus urinary bladders stripped of serosal muscle and connective tissue
were impaled through their basolateral membranes with microelectrodes in
experiments that permitted rapid changes in the ion composition of the
serosal solution. The transepithelial electrical properties exhibited a
marked seasonal variation that could be attributed to variations in the
conductance of the shunt pathway, apical membrane selectivity, and
basolateral Na+ transport. In contrast, the passive electrical properties
of the basolateral membrane remained constant throughout the year. The
apparent transference numbers (Ti) of the basolateral membrane for K+ and
Cl- were determined from the effect on the basolateral membrane equivalent
electromotive force of a sudden increase in the serosal K+ concentration
from 2.5 to 50 mM/liter or a decrease in the Cl- concentration from 101 to
10 mM/liter. TK and TCl were 0.71 +/- 0.05 and 0.04 +/- 0.01, respectively.
The basolateral K+ conductance could be blocked by Ba2+ (0.5 mM), Cs+ (10
mM), or Rb+ (10 mM), but was unaffected by 3,4- diaminopyridine (100
microM), decamethonium (100 microM), or tetraethylammonium (10 mM). We
conclude that a highly selective K+ conductance dominates the electrical
properties of the basolateral membrane and that this conductance is
different from those found in nerve and muscle membranes.
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