Cellular Mechanisms in Acid Secretion

The secretion of acid by the upper gastrointestinal tract first appeared among the lowest vertebrates on the phylogenetic tree and has since been retained by most species (1). The obvious physiological role for this acid is in the digestion of food by pepsin; however the importance of acid-peptic digestion in man appears quite limited in light of the normal nutritional status of persons with achlorhydria. The stomach may have retained the ability to secrete acid not primarily for digestion, but rather to sterilize the upper gastrointestinal tract. Although secretion of acid appears to be a dispensable function in man, acid does play a major role in the pathophysiology of peptic ulcer disease and of most of the bleeding disorders of the upper gastrointestinal tract. This review concerns our current, admittedly limited, knowledge of the cellular mechanisms of gastric acid secretion. It attempts to lay a groundwork for understanding certain aspects of acid-peptic disorders, particularly the pathophysiology and the mechanisms underlying the effectiveness of some of the therapeutic modalities used.