AJP - Cell Physiology, Vol 232, Issue 3 99-108, Copyright © 1977 by American Physiological Society
Effects of luminal hyperosmolality on electrical pathways of Necturas gallbladder
L. Reuss and A. L. Finn
The electrical properties of the transepithelial pathways of Necturaus
gallbladder were studied with intracellular microelectrode techniques under
control conditions and after exposure to hyperosmotic mucosal bathing media
(addition of sucrose or other solutes). Doubling mucosal osmolality
produces a large increase in the resistance of the intercellular shunt
pathway (from 420 +/- 50 to 700 +/- 70 omega - cm2, P is less than 0.001)
and a significant decrease in the resistance of the apical membrane of the
cells (from 3,510 +/- 420 to 1,540 +/- 380 omega p cm2, P is less than
0.001). The basolateral membrane resistance remains unchanged. Both the
apical and basolateral membranes depolarize (from 59.5 +/- 1.8 to 36.6 +/-
2.8 mV, P less than 0.0001, and from 61.8 +/- 1.7 to 32.2 +/- 3.0 mV,P is
less than 0.001, respectively). The transepithelial diffusion potential
resulting from NaCl concentration gradients due to the osmotic water flow
does not explain the cell potential changes. Mucosal solution ion
substitution experiments demonstrate increases of gk, gcl, and gna (ca.
2.5-fold, 4-fold, and 7-fold, respectively). Therefore, cell depolarization
appears to be produced mainly by a reduction of apical membrane K
permselectivity. The increase in the resistance of the shunt is
attributable to reduction of the width of the lateral intercellular spaces,
because of the osmotic serosa-to-mucosa water flow.
