ABSTRACT
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.
Subject(s)
Chlorides/pharmacology , Gallbladder/physiology , Animals , Anions , Cations, Divalent , Cell Membrane/drug effects , Cell Membrane/physiology , Cyclamates/pharmacology , Epithelium/drug effects , Epithelium/physiology , Gluconates/pharmacology , Guinea Pigs , In Vitro Techniques , Isethionic Acid/pharmacology , Male , Membrane Potentials/drug effects , Sulfates/pharmacologyABSTRACT
The measurement of chloride activity was studied with Cl- -sensitive ion-exchanger microelectrodes (ISE) in calibrated test solutions stained with commonly used renal test dyes (e.g. Lissamine green SF) or other food or cosmetic dyes. Renal test dyes impair measurements of Cl- activity due to their anionic substitution and were found to increase electrode resistance. Cationic food dyes did not interfere with the Cl- reading of ISE although electrode resistances were increased, too.