Inhibition of carbonic anhydrase by pirenzepine

Previous work of the authors established a parallelism between gastric mucosa carbonic anhydrase (CA) activity and the values of acid secretion. It was shown that histamine (Ht) is a physiological activator of CA, and that there could be histaminic H2 receptors located on the molecule of CA. Pirenzepine (GZ) is a drug recently introduced in the therapy of gastroduodenal ulcer (GDU). Although its effect of decreasing acid secretion is clinically known, its mechanism of action remains uncertain. Original investigations are presented proving by in vitro and in vivo experiments on pure CA and on CA from human red blood cells and gastric mucosa that GZ is a strong inhibitor of CA. In this concept, GZ may be considered both an enzymatic inhibitor and an antagonist of histaminic H2 receptors.