References j 63 



tion is correspondingly low. In overall composition, it resembles 

 much more closely the pancreatic secretion of other mammals 

 rather than saliva. Despite these differences, it resembles other 

 salivas in having a potassium concentration that is higher than the 

 serum level and a positive dependence of sodium and bicarbonate 

 on flow rate. Potassium, chloride and phosphate, however, are 

 negatively dependent on flow rate. Very well marked transient 

 concentrations of all the ions are seen when the flow of saliva is 

 increased above the basal level by nerve stimulation or the intra- 

 arterial injection of acetylcholine. 



The most interesting feature of the gland is the very striking 

 change in saliva composition produced by variations in adreno- 

 cortical function. If a sheep with a parotid fistula is placed on a low 

 sodium intake, it rapidly becomes sodium-depleted due to the 

 losses in the saliva. The endogenous secretion of mineralocorticoids 

 is thereby stimulated and these lead to a change in the composition 

 of the saliva such that sodium is almost entirely replaced by potas- 

 sium. In the repleted state, the saliva may contain 10 mEq/1. of 

 potassium and 190 mEq/1. sodium, but after 4-5 days of sodium 

 depletion, the saliva potassium commonly rises to 140 mEq/1. and 

 the sodium falls to less than 60 mEq/1. (Fig. 8.12). This change 

 does not occur in adrenalectomized sheep maintained on deoxy- 

 cortone. The effects of sodium depletion can be rapidly reversed 

 by an intravenous infusion of sodium chloride ; correction of the 

 salivary electrolytes composition begins after a latent period of 

 about an hour. These cation changes occur in the absence of any 

 significant alterations in the anion composition. The parotid gland 

 of the sheep appears to be a very sensitive assay preparation for 

 mineralocorticoids (Denton, 1956, 19570, b; Coats and Wright, 

 1957; Denton and McDonald, 1956; Goding and Denton, 1956). 



REFERENCES 



Anderson, d. j. (1949). The hydrogen ion concentration of saliva. J', dent. 

 Res., 28, 583-588. 



Andreyev, L. and L. I. pugsley (1933)- The effects of parathyroid hormone 

 and of irradiated ergosterol upon the calcium content of the parotid 

 saliva of the dog. J. Physiol., 86, 98. 



awwad, H. K. (1959). The influence of x-irradiation on the iodide-trap- 

 ping mechanism of the human parotid gland. Brit. jf. Radiol., 32, 

 259-262. 



