146 The Inorganic Components of Saliva 



found the bicarbonate in the sublingual saliva of dogs to average 

 only 5-2 mEq/1. and not to be changed appreciably with flow 

 rate. 



The literature describing the relationship between the concen- 

 tration of bicarbonate in plasma and saliva is rather confusing. 

 For instance, de Beer and Wilson (1932) in the dog parotid gland 

 stimulated by pilocarpine, found that on raising the plasma bicar- 

 bonate by an infusion of sodium carbonate, the saliva bicarbonate 

 rose about proportionally, but continued to rise at a time when the 

 plasma bicarbonate was falling. 



McClanahan and Amberson (1935) found a linear relationship 

 between plasma and saliva bicarbonate in the cat submaxillary 

 gland but an unexplained feature of their experiments was that 

 whereas the saliva bicarbonate was approximately equal to the 

 plasma level in those experiments in which saliva secretion was 

 caused by chorda stimulation, it was twice as great in those in 

 which pilocarpine was used. In some of the experiments in this 

 same paper in which perfused submaxillary glands were used, the 

 proportionality between plasma and saliva concentration is much 

 less clear. For instance, in one experiment when the plasma level 

 was raised from 12-9 mEq/1. to 20-9 mEq/1. the saliva concentra- 

 tion remained unchanged! Sand (1951) found no satisfactory corre- 

 lation between the saliva and plasma bicarbonate in man after 

 ingestion of ammonium chloride. Wechsler (1959) also found 

 the response to sodium bicarbonate administration to be unpre- 

 dictable. 



The elucidation of this confusing situation has come about 

 through the study of the effects of change in pC0 2 on the saliva 

 bicarbonate (Burgen, i960). In dog parotid saliva the bicarbonate 

 saliva/plasma ratio (s/p) is directly dependent on the arterial 

 pC0 2 . In the experiment shown in Fig. 8.5 when the arterial pC0 2 

 was reduced from 38 mm Hg to 11-5 mm Hg, by hyperventilation, 

 the bicarbonate s/p fell from 278 to 1-25 and, conversely, when 

 the pC0 2 was raised by inhalation of 10 per cent carbon dioxide in 

 oxygen the saliva s/p rose to 3-8. When the plasma bicarbonate 

 level was increased by infusion of sodium bicarbonate the s/p 

 remained more or less unchanged when it was compared with the 

 s/p for the corresponding pC0 2 before the infusion. The irregu- 

 larities in the results reported in the literature are therefore probably 

 due to the compensatory changes in pC0 2 which are consequent 



