Alteration of alpha-amylase secretion from rat parotid cells in the absence of extracellular bicarbonate.

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 alpha-amylase secretion, as well as carbamylcholine- and isoproterenol-stimulated alpha-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.