Parietal cell - Definition and Overview

Parietal cells (also called oxyntic cells) are cells located in the stomach epithelium.

Acid production

Parietal cells produce gastric acid (hydrochloric acid). This maintains the acidic environment needed by gastric enzymes.

Parietal cells secrete acid in response to three types of stimuli: -

• parasympathetic activity via the Vagus nerve
• H₂ histamine receptors
• gastrin

Upon stimulation, adenylate cyclase is activated within the parietal cells. This increases intracellular cyclic AMP, which leads to activation of protein kinase A. Protein kinase A phosphorylates proteins involved in the transport of H⁺/K⁺ ATPase from the cytoplasm to the cell membrane. This causes resorption of K⁺ ions and secretion of H⁺ ions. The pH of the secreted fluid can fall to 0.8 .

Intrinsic factor

Parietal cells also produce intrinsic factor. Intrinsic factor is required for the absorption of vitamin B12 in the diet.

Diseases of parietal cells

• Peptic ulcers can result from over-acidity in the stomach. Antacids can be used to enhance the natural tolerance of the gastric lining. Antimuscarinic drugs such as pirenzepine or H₂ antihistamines can reduce acid secretion. Proton pump inhibitors are more potent at reducing gastric acid production.

• In pernicious anemia, autoantibodies directed against parietal cells or intrinsic factor cause a reduction in vitamin B12 absorption. It can be treated with injections of replacement vitamin B12 (hydroxocobalamin or cyanocobalamin).

• Achlorhydria is another autoimmune disease of the parietal cells. The damaged parietal cells are unable to produce the required amount of gastric acid. This leads to an increase in gastric pH, impaired digestion of food and increased risk of gastroenteritis.