1 82 Organic Constituents of Saliva 



to those produced by the dog, are formed by slices of the rat sub- 

 maxillary gland in vitro (Taurog, Potter, Tong and Chaikoff, 

 1956). An iodine protein apparently similar to that present in the 

 saliva has been found in milk from several species (Brown-Grant 

 and Galton, 1958). 



TOTAL PROTEIN SECRETION 



It has been known for a long time that the concentration of 

 protein in the saliva is in general dependent on the rate of saliva 

 secretion, and also that the concentration in the saliva is progres- 

 sively lowered during prolonged stimulation of the salivary gland 

 (Heidenhain, 1883; Langley, 1898). Anrep (1921) found that the 

 protein concentration in the saliva from the submaxillary gland of 

 the dog fell exponentially with the duration of stimulation (Fig. 9.4), 

 a circumstance that is to be expected if the rate of protein syn- 

 thesis by the gland is very low compared with the rate of protein 

 secretion, so that secretion represents (for a given rate of nerve 

 stimulation) removal of a fixed fraction of the available proteins 

 stored in the gland per unit time. Anrep's experiments showed 

 that about 20 per cent of the protein nitrogen of the resting gland 

 was available for secretion; similar results have been obtained in 

 the dog parotid (Burgen, Weiss and Seeman, 1959). Anrep and 

 Khan (1923) found that restitution of the protein content of the 

 saliva was very slow, needing some 48 to 72 hours for completion. 

 Langstroth, McRae and Stavraky (19380) provided an empirical 

 mathematical basis for following the concentration of protein in 

 the saliva at different phases of secretion. Stavraky (1940) pointed 

 out that after prolonged stimulation the concentration of protein 

 in saliva does not fall to zero but reaches a steady state presumably 

 determined by a balance between the rate of synthesis and secretion 

 of protein. 



In Fig. 9.5 is seen a typical relationship between protein output 

 and the flow of saliva. The concentration in the saliva rises more 

 or less linearly with flow so that the total output of protein per 

 unit time rises steeply with flow rate. The output of protein is not 

 necessarily related to the flow of saliva but is rather a direct func- 

 tion of the stimulation of the gland. The following fact illustrates 

 this: in a dog parotid gland the maximum rate of saliva flow is 

 usually produced when the rate of stimulation of the auriculo- 

 temporal nerve reaches 20 to 30 c/s, but further increase in fre- 



