Metalloporphyrin chloride ionophores: evidence for induction of
increased anion permeability in cultured human and mouse lung
epithelial cells.
El-Etri, Mohamed, and John Cuppoletti.
Department of Molecular and Cellular Physiology and Department of
Internal Medicine, University of Cincinnati College of Medicine,
Cincinnati, OH 45267-0576
APStracts 2:0179L, 1995.
5,10,15,20-tetraphenyl-21H,23H-porphine manganese(III) chloride
[TPPMn(III)] is a positively charged lipophilic anion carrier which
is widely used as a Cl- sensor. TPPMn(III) increased anion
permeability of cultured mouse lung epithelial (MLE) cells as
measured by short circuit current (SCC) to a level similar to that
induced by forskolin analogs. Anion permeability was also studied in
cultured human lung epithelial (A549) cells by measurement of the
rates of change of fluorescence of the anion sensitive fluorescent
dye, 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ). In these studies,
cells were incubated with SPQ in SO42- medium, washed free of
extracellular SPQ and then perfused with medium containing anions
which are known to quench SPQ fluorescence. The effect of TPPMn(III)
on anion transport was then determined either microscopically in
single cell studies or using cell monolayers mounted in a front-face
fluorimeter. TPPMn(III) in the range from 1 to 100 [mu]g/mL induced a
dose-dependent increase in Br- transport. The half-maximal quenching
effect was estimated to be approximately 5 [mu]g/mL. TPPMn(III)
increased the rates of fluorescence quench of anions by up to 4 fold.
TPPMn(III) was without effect on [Ca2+]i level in A549 cells as
measured with fura-2/AM. This indicates that TPPMn(III) effects were
not mediated through effects on Ca2+-activated Cl- channels, or by
compromise of energy metabolism or membrane integrity of the cells.
This study suggests that TPPMn(III) and by extension, other
lipophilic Mn(III) or Co(III) derivatives wherein the selectivity or
lipophilicity is altered, could increase the anion permeability of
biological membranes, and suggests a new approach for treatment of
diseases such as cystic fibrosis, where transport of Cl- is
defective.
Received 26 Juen 1995; accepted in final form 2 October 1995.
APS Manuscript Number L199-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95