Histochemical localization of carbonic anhydrase in the pig's exocrine pancreas.

Carbonic anhydrase is essential for the pancreatic secretion of NaHCO3. To localize the distribution of carbonic anhydrase in the exocrine gland and, hence, identify the potential cellular source of secreted NaHCO3, histochemical staining of carbonic anhydrase was carried out on pancreatic biopsies obtained from six pigs at both supramaximal intravenous secretin stimulation and at secretory rest. Tissue staining, using Hansson's technique, revealed a strong staining both in membranes and cytoplasm in the duct cells and a weaker cytoplasmic staining in the acinar cells. Staining reaction was abolished by 10(-5) mol l-1 acetazolamide. Duct cells, accordingly, seem to be responsible for NaHCO3 secretion, while acinar cells appear unlikely to contribute substantially to NaHCO3 secretion.