pH and Bicarbonate Concentration 147 



on a metabolic alkalosis or acidosis. Sand (1949) has shown that 

 the pC0 2 is independent of saliva secretion rate and closely follows 

 the arterial pC0 2 although it is usually 20-30 per cent higher. 

 Because of this, the saliva pH changes little when the arterial pC0 2 

 is changed because both the pC0 2 and bicarbonate of the saliva are 

 changed in the same direction nearly proportionately. In a careful 

 study of human parotid saliva Chauncey and Weiss (1958) were 

 unable to demonstrate any effect of quite large doses (4'8-22mg/kg) 

 of the potent carbonic anhydrase inhibitor acetazoleamide (Dia- 

 mox) on either salivary bicarbonate or pH. Negative results were 



-4 





80 





60- 



* 401 

 ^ 20- 



-5 

 •2 

 -/ 



HC0 5 



Saliva 



Plasma 



20 40 60 80 

 p CO 2 mm Hg 



Fig. 8.5. The effect of change of pC0 2 on the concentration of bicarbonate 



in the saliva. 



The saliva /plasma ratio is increased by a rise in arterial pCO,. The open symbols were values 

 obtained after intravenous injection of 10 mEq/kg of NaHC0 3 . The plasma and saliva bicarbon- 

 ate both increased but the saliva/plasma ratio did not change. 



also obtained by Niedermeier, Stone, Dreizen and Spies (1955) 

 and Burgen (i960). 



Saliva produced in the cat submaxillary gland by sympathetic 

 nerve stimulation has a much higher bicarbonate concentration 

 than chorda saliva (Langstroth, McRae and Stavraky, 19386). 

 This higher bicarbonate concentration is accompanied by a higher 

 sodium and potassium concentration but by little change in the 

 chloride. Similar changes are produced by adrenaline. On the 

 other hand, large doses of adrenaline produce long-lasting after- 

 effects on the sodium and chloride concentrations in chorda saliva 

 but only trivial changes in the bicarbonate. 



