acid secretion

Definition

Target type: biologicalprocess

The controlled release of acid by a cell or a tissue. [GOC:ai]

Acid secretion is a fundamental biological process that involves the movement of hydrogen ions (H+) across a cell membrane, leading to a decrease in pH of the surrounding environment. This process is essential for various physiological functions, including digestion, pH regulation, and defense against pathogens.

The mechanism of acid secretion varies depending on the type of cell and the specific organ involved. In the stomach, for instance, parietal cells are responsible for the production and secretion of hydrochloric acid (HCl). This process is regulated by a complex interplay of signaling molecules and membrane transport proteins.

**1. Activation of Parietal Cells:**
- Gastrin, a hormone released by the stomach lining, stimulates parietal cells via the G protein-coupled receptor (GPCR) pathway.
- Histamine, a neurotransmitter, also activates parietal cells through H2 receptors.
- Acetylcholine, released by the vagus nerve, activates parietal cells through muscarinic receptors.

**2. Intracellular Signaling:**
- Activation of GPCRs leads to the activation of adenylyl cyclase, which converts ATP into cyclic adenosine monophosphate (cAMP).
- cAMP activates protein kinase A (PKA), which phosphorylates various target proteins involved in acid secretion.

**3. Proton Pump Activation:**
- PKA phosphorylation leads to the translocation of H+/K+ ATPase (proton pump) to the apical membrane of the parietal cell.
- The proton pump is a transmembrane protein that actively pumps H+ ions from the cytosol into the stomach lumen, exchanging them for potassium ions (K+).

**4. Chloride Ion Transport:**
- The secretion of H+ ions is accompanied by the movement of chloride ions (Cl-) through chloride channels.
- This process is crucial to maintain electrical neutrality and ensure the effective secretion of HCl.

**5. Acid Secretion:**
- The combined movement of H+ and Cl- ions results in the secretion of HCl into the stomach lumen, leading to the acidic environment necessary for digestion.

**Regulation of Acid Secretion:**
- Acid secretion is tightly regulated to prevent damage to the stomach lining and ensure optimal digestion.
- Negative feedback mechanisms, such as the presence of acidic chyme in the duodenum, trigger the release of hormones like somatostatin, which inhibits gastric acid secretion.

**Other Acid Secretion Mechanisms:**
- In other tissues, such as the kidneys, acid secretion occurs through different mechanisms.
- For example, renal tubular cells utilize proton pumps and other transporters to regulate the pH of urine and maintain electrolyte balance.'
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Proteins (3)

Compounds (349)