WATER PERMEABILITY AND SALT REABSORPTION IN THE DUCT SYSTEM OF THE SUBMAXILLARY GLAND OF DOGS
1972 Volume 22 Issue 3 Pages 271-280
Details
1972 Volume 22 Issue 3 Pages 271-280
1. The reabsorptive function of salivation at the duct system of the dog's submaxillary gland was studied in this experiment, where control salivation was initiated by stimulation of the chorda tympani, and experimental salivation was initiated by simultaneous stimulation of the perivascular nerve and the chorda tympani.
2. Osmotic concentration of the experimental saliva was relatively higher than that of the control saliva. The causal factors in the relative rise of saliva osmolality were analyzed by estimation of salt reabsorption and the increment of water permeability at the duct system.
3. Reabsorption of 22Na at the duct system was measured as an index of the reabsorptive rate of salt. The reabsorption of 22Na was not affected by stimulation of the chorda tympani and was assumed to be a constant value under this experimental condition.
4. The reabsorptive rate of 22Na was decreased to 60-75% of the control by stimulation of the perivascular nerve.
5. It was found theoretically that the relationship between the flow rate of saliva (V) and the ratio of osmotic concentration of saliva to plasma (Sosm/Posm) can be explained by the relation found in a rectangular hyperbolic curve.
6. From the hyperbolic curves which were fitted by inspection to the plots from the actual measurements it was demonstrated that, in experimental salivation, the reabsorptive rate of salt decreased to 60% of the control, the osmotic permeability for water increased to 140%, and the hydrostatic permeability for water increased to 250% at the duct system of the submaxillary gland.
7. Thus the increase of salt concentration in experimental saliva is concluded to be initiated by a decreased osmotic tonicity of fluid reabsorbed through the duct.
