AJP - Cell Physiology, Vol 257, Issue 4 C766-C774, Copyright © 1989 by American Physiological Society
Membrane effects of chloride substitutes in guinea pig gallbladder epithelial cells
F. Wehner, G. Sigrist and K. U. Petersen
Institut fur Pharmakologie der Medizinischen Fakultat, Rheinisch-Westfalische, Technische Hochschule Aachen, Federal Republic of Germany.
Differences in the responses of guinea pig gallbladder epithelial cells to
replacement of luminal Cl- with either isethionate (I), gluconate (G),
sulfate (S), or cyclamate (C) were investigated in vitro using
intracellular microelectrode techniques. In prostaglandin E1 (PGE1)-treated
tissues (10(-6) M, serosal side), where electrodiffusive apical membrane
Cl- permeability (PCla) is high, replacement of luminal Cl- caused
transient membrane depolarizations of similar magnitudes but different
times to peak (C greater than G = S greater than I). The subsequent shifts
in membrane voltages were, at steady state, straight correlated with the
concomitant increases in apparent ratio of apical to basolateral membrane
resistances (Ra/Rb). Increases followed the rank order I greater than G = S
greater than C, which was also found to be the case in the peak membrane
hyperpolarizations on restoring luminal Cl-. Under control conditions (no
PGE1, low PCla), three of the substitutes caused a slow hyperpolarization,
C greater than G = S, whereas an I-for-Cl- substitution evoked a transient
depolarization and a drop in Ra/Rb. Under both control and PGE1 conditions,
a transient depolarization followed luminal I-for-C substitution. Our
results are best explained by a stimulatory effect of I (and, less marked,
G and S) on PCla. Intrinsic effects of cyclamate are not ruled out;
however, among the substitutes examined, it is the most inert.
