A sufficient availability of the bicarbonate anion is required to allow a normal process of glucose-stimulated insulin release. Thus, both the removal of extracellular bicarbonate and the inhibition of carbonic anhydrase by acetazolamide suppress the insulinotropic action of glucose. In the present study, a comparable situation is documented in rat parotid cells. Thus, the absence of extracellular bicarbonate is shown to decrease by about 50% basal α-amylase secretion, as well as carbamylcholine- and isoproterenol-stimulated α-amylase output, without suppressing the enhancing action of the two agents. It is proposed, therefore, that the HCO3−anion participates in the secretory sequence at sites distal to the identification of secretagogues in both endocrine and exocrine cells.

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