AJP - Renal Physiology, Vol 266, Issue 2 259-F265, Copyright © 1994 by American Physiological Society
Conductive properties of papillary surface epithelium
W. B. Reeves
Division of Nephrology, University of Arkansas for Medical Sciences, Little Rock 72205.
The surface epithelium of rabbit renal papilla was dissected free from its
supporting tissue and mounted in an Ussing chamber. The conductive
properties of the epithelium and of the apical and basolateral cell
membranes were examined with KCl-filled microelectrodes. The
transepithelial voltage was 0.07 +/- 0.15 mV, and the transepithelial
resistance was 107 +/- 15 omega.cm2 (n = 29). The fractional resistance of
the apical membrane (fRa) was 0.93 +/- 0.01 (n = 103 cells, 29 tissues).
The apical membrane was not conductive to Na+, K+, or Cl-. An increase in
the K+ concentration of the basolateral solution from 5 to 50 mM
depolarized the basolateral membrane voltage (Vb) from -59 +/- 1.6 to -31.2
+/- 2.2 mV (n = 28 cells) and increased fRa from 0.935 +/- 0.01 to 0.962
+/- 0.01 (P < 0.001, n = 21 cells). Likewise, 5 mM barium in the
basolateral solution depolarized Vb from -57.7 +/- 2.0 to -29.8 +/- 2.2 mV
(n = 21 cells). A tenfold decrease in the Cl- concentration of the
basolateral solution caused an 8.3 +/- 1.9 mV depolarization in Vb. Thus
the basolateral cell membrane is conductive to K+ and Cl-. Exposure of the
apical membrane to amphotericin B demonstrated that the transepithelial
resistance is determined primarily by the paracellular pathway.
