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Biophys J, August 2001, p. 852-866, Vol. 81, No. 2

PGE2 Activation of Apical Membrane Clminus Channels in A6 Epithelia: Impedance Analysis

Teodor G. Păunescu and Sandy I. Helman

Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 USA

Measurements of transepithelial electrical impedance of continuously short-circuited A6 epithelia were made at audio frequencies (0.244 Hz to 10.45 kHz) to investigate the time course and extent to which prostaglandin E2 (PGE2) modulates Cl- transport and apical membrane capacitance in this cell-cultured model epithelium. Apical and basolateral membrane resistances were determined by nonlinear curve-fitting of the impedance vectors at relatively low frequencies (<50 Hz) to equations (Păunescu, T. G., and S. I. Helman. 2001. Biophys. J. 81:838-851) where depressed Nyquist impedance semicircles were characteristic of the membrane impedances under control Na+-transporting and amiloride-inhibited conditions. In all tissues (control, amiloride-blocked, and amiloride-blocked and furosemide-pretreated), PGE2 caused relatively small (<~3 µA/cm2) and rapid (<60 s) maximal increase of chloride current due to activation of a rather large increase of apical membrane conductance that preceded significant activation of Na+ transport through amiloride-sensitive epithelial Na+ channels (ENaCs). Apical membrane capacitance was frequency-dependent with a Cole-Cole dielectric dispersion whose relaxation frequency was near 150 Hz. Analysis of the time-dependent changes of the complex frequency-dependent equivalent capacitance of the cells at frequencies >1.5 kHz revealed that the mean 9.8% increase of capacitance caused by PGE2 was not correlated in time with activation of chloride conductance, but rather correlated with activation of apical membrane Na+ transport.

Biophys J, August 2001, p. 852-866, Vol. 81, No. 2
© 2001 by the Biophysical Society   0006-3495/01/08/852/15  $2.00


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