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Regulation of 86 Rb + ion transport across polarized human colonocytes by bis‐phenolic compounds
Author(s) -
Mason Robert W,
SimpsonSmall Tiffani,
Hopp Laszlo
Publication year - 2003
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1046/j.1440-1681.2003.03890.x
Subject(s) - phenolphthalein , efflux , chemistry , ouabain , apical membrane , ion transporter , intracellular , stimulation , biophysics , epithelial polarity , atpase , biochemistry , sodium , cell , membrane , biology , enzyme , endocrinology , organic chemistry
Summary 1. Phenolphthalein, a well‐known laxative, stimulates the secretion of Na + and Cl – ions and accompanying water into the intestinal tract. Measurement of 86 Rb + efflux from several, but not all, cell types indicates that phenolphthalein also results in release of cellular K + ions. 2. In the present study, the transport of 86 Rb + across human colonocyte cells (T84) cultured on trans ‐well inserts was examined. The T84 cells were cultured until they developed tight junctions and a high trans ‐epithelial resistance. 3. Results show that phenolphthalein applied to the apical, but not the basolateral, surface of cells causes the release of 86 Rb + from the apical surface. Basolateral treatment of cells with phenolphthalein had no effect on the release of 86 Rb + . 4. Simultaneously with the increased 86 Rb + efflux, indirect evidence of enhanced Na + /K + ‐ATPase activity was also observed. 5. Although ouabain inhibited the increased Na + pump activity, it did not affect apical 86 Rb + release. 6. As evidenced by near steady state 86 Rb + uptake data, the increased Na + /K + ‐ATPase activity was insufficient to restore intracellular concentrations of K + in the presence of phenolphthalein. 7. 4,4(9‐Fluorenylidene)diphenol, a homologue of phenolphthalein, had a similar effect on 86 Rb + transport by T84 cells. 8. These results indicate a primary stimulation of 86 Rb + efflux from the apical surface of polarized T84 cells by apically applied bis‐phenolic compounds. 9. A secondary stimulation of the basolateral Na + /K + ‐ATPase is thought to result from intracellular Na + increase, as documented in several other cell types exposed to bis‐phenolic compounds, although not directly measured in these experiments. 10. The results also indicate that bis‐phenolic compounds interact specifically with some apical but not basolateral membrane structures in regulating 86 Rb + efflux from polarized T84 cells.