The effect of carbonic anhydrase inhibitors on the anionic composition of sheep's parotid saliva. With an appendix on uncatalysed carbon dioxide‐water kinetics by P. T. McTigue.

1. The effects of the carbonic anhydrase inhibitors, acetazolamide, ethoxzolamide and benzolamide on the ionic composition of parotid saliva were studied in anaesthetized sheep with access to the parotid blood vessels. 2. The inhibitors were infused directly into the arterial blood supply to the gland to give blood concentrations in the range 10(‐5) to 10(‐2) M. 3. Mean anionic concentrations at basal flow rate before inhibitor infusion were, bicarbonate 98 m‐mole/l., phosphate 15 m‐mole/l. and chloride 26 m‐mole/l. In the presence of inhibitors, bicarbonate concentration fell by 11 m‐mole/ml. and phosphate and chloride concentrations rose. Secreto‐motor nerve stimulation increased bicarbonate concentration by 13 m‐mole/l. before infusion of inhibitors and the concentrations of the other anions fell. The bicarbonate rise was abolished by the inhibitors and the fall in phosphate concentration was balanced by a rise in chloride concentration. 4. These effects show that only a small component of the bicarbonate ion transfer system in the sheep parotid gland is sensitive to these inhibitors. 5. The relationship of these findings to a new enzyme with carbonic anhydrase action isolated from the sheep's parotid gland is discussed.