Water Flux Rates Across Dog Gallbladder Wall

Abstract

Net and one-way flux rates of water across the dog gallbladder wall were measured by filling the organ with D₂O enriched sodium chloride solutions of different osmotic activities and observing changes in volume and isotope concentration. Net flux rates out of the organ were found to be inversely proportional to the sodium concentration of the lumenal fluid, being 86 µl/min. at 70 mEq/l., zero at 220 mEq/l. and –121 at 421 mEq/l. One-way outflux rates decrease with increasing sodium concentration but not linearly; values of the order of 200–260 µl/min. were found. One-way influx rates are equal for hypotonic and isotonic solutions, but nearly double for hypertonic fluid. Comparison was made of water flux rates across the gallbladder wall with published data on dog ileum and urinary bladder, all appropriately corrected for mucosal surface area. On this basis, gallbladder mucosa seems to have the greatest absorptive capacity, and gallbladder and urinary bladder both seem to have greater permittivity to water than the ileum. The apparent higher water permittivity and absorptive capacity of ileum must be attributed to a much greater total mucosal surface area.