Total Osmolyte Concentration 143 



secreted by the cat submaxillary gland in response to sympathetic 

 stimulation, has a higher osmolarity than chorda saliva; after a 

 large dose of adrenaline, the osmolarity of subsequently secreted 

 chorda saliva is considerably increased (Langstroth, McRae and 

 Stavraky, 19386). 



The production of hypotonicity is one of the most interesting 

 and elusive phenomena in salivary secretion. The total amount of 

 osmotic work that the gland can perform is not great (average for 

 the dog parotid 137 m.cal/g. min) compared with the total energy 



so 



260 

 220 

 180 

 MO 

 WO 

 60 

 20 







Os molarity 



I 1 1 1 1 1 1 1 1 1 1 1 1— T" 



100 200 300 400 500 600 700 



Fate (mg saliva /g gland /min 



Fig. 8.3. Osmolarity of parotid saliva in the dog at different 

 rates of saliva secretion. 

 (Brusilow and Cooke, 1959-) 



production of the gland and it seems most improbable that the 

 performance of osmotic work is a limiting factor in the secretory 

 process (Burgen, 1955). Japelli (1906) made the interesting obser- 

 vation that when the plasma osmolarity of the dog was raised by 

 injection of 10 per cent sodium chloride solution intravenously, 

 there was an increase in saliva osmolarity although it was not 

 necessarily proportionate. He also found that the freezing point 

 depression of gland homogenates was identical to that of the plasma. 

 Recently it has been found that in man, dehydration and subse- 

 quent repletion by water drinking leads to corresponding changes 

 in the saliva osmolarity (Friedberg and Doyle, 1959). 



Burgen (19566) has suggested that some water reabsorption 



