A mechanism for absorption of sodium chloride solutions from the canine gall bladder

¹ Department of Physiology, University of Minnesota, Minneapolis, Minnesota

Absorption of NaCl solutions of different concentrations and of autogenous plasma from the canine gall bladder was studied. Net water flux was linearly related to osmotic activity of the luminal solution, and was positive (in the direction, lumen to blood) up to 420 mOs/liter. Net Na and Cl fluxes were positive above luminal concentrations of 90 and 65 mEq/liter, respectively, and rose with increasing concentration up to that point at which net water flux changed direction; beyond this, they remained essentially constant. Several models for the transport mechanism were considered, with particular emphasis on the question of passive versus active water transport. The only one which was reasonably consistent with experimental observation was as follows. Active transport of solution from lumen to blood by a solution pump like pinocytosis occurred at a rate independent of luminal concentration. The remainder of the water flux was as bulk flow due to the osmotic gradient. Na and Cl transport could be entirely accounted for by movement in the "pinocytotic" fluid and by diffusion in the convective field arising from the osmotic transport of water.

Note:
With the Technical Assistance of Joan Moran and Alberta J. Neal