Journal of Applied Physiology, Vol 51, Issue 2 363-368, Copyright © 1981 by American Physiological Society
Nonelectrolyte permeability of canine tracheal epithelium
S. F. Man and B. R. Thomson
We examined the nonelectrolyte permeability characteristics of canine
tracheal epithelium in vitro and confirmed that the transepithelial
potential difference was 26.3 +/- 2.2 mV, lumen negative. Exposure of the
epithelium to a sucrose osmotic load resulted in a streaming potential
(SP); a linear relationship was noted between osmotic load and SP. The
presence of an osmotic load did not change the short-circuit current and
the SP disappeared after removal of the osmotic load. The SP developed with
urea, thiourea, D-xylose, and l-glycine were similar to the SP developed
for equimolar concentrations of sucrose. The urea and insulin spaces were
similar magnitude. When the bulk phase was stirred at 600 rpm, the
effective thickness of the unstirred water layer (UWL) external to the
epithelial surface was 144 +/- 12 micron. These results support the
suggestion that the Staverman reflection coefficients (sigma) of these
probe molecules are similar, the estimates of sigma are valid despite the
presence of an UWL, and the tracheobronchial epithelium has a pore size
smaller than the hydrodynamic radius of urea.
