chief cell

**Chief cells (Gastric)**

**Location:** Base of gastric glands (fundus and body) of the stomach. Not to be confused with parathyroid chief cells.

**Histology:** Basophilic cytoplasm (abundant rough ER) basally; apical eosinophilic zymogen granules. Features of a protein-secreting cell. Contrast with parietal cells, which are eosinophilic (abundant mitochondria) with an intracellular canalicular system.

**Products:** - Pepsinogen (zymogen), which is activated to pepsin by low pH (HCl) and then by autocatalysis. Pepsin digests proteins and works best at an acidic pH. - Gastric lipase, which digests some dietary triglycerides.

**Regulation of secretion:** - Stimulated by vagal ACh (M3 receptors). - Stimulated by low luminal pH, through local enteric reflexes and secretin. - Stimulated by gastrin and histamine (minor effect). - Because acid is needed to activate pepsinogen, anything that raises pH (PPIs, atrophic gastritis) reduces pepsin activity.

**Clinical correlations:** - Chronic atrophic gastritis (autoimmune type A, in the body and fundus) destroys parietal and chief cells. This causes hypochlorhydria, hypergastrinemia, low intrinsic factor, and pernicious anemia (B12 deficiency). - Serum pepsinogen I level and the pepsinogen I/II ratio fall with atrophic body-predominant gastritis, so they are used as a marker. - Zollinger-Ellison syndrome (gastrinoma) raises acid and pepsin output, causing refractory peptic ulcers. - Chief cells can transdifferentiate into spasmolytic polypeptide-expressing metaplasia (SPEM) in chronic injury, and are a proposed precursor of intestinal metaplasia.

**Other cell types in the gastric gland (high-yield comparison):** - Mucous neck cells: mucus (bicarbonate-rich). - Parietal cells: HCl and intrinsic factor. - Enterochromaffin-like (ECL) cells: histamine. - G cells (antrum): gastrin. - D cells: somatostatin.

**Mnemonic:** Chief cells = "Pepsinogen, Powered by the vagus and acid." Think "Chief = Chunk of protein digestion" (pepsin cleaves proteins). Parietal cells make acid and intrinsic factor.

**Note:** Parathyroid chief cells are a different cell type. They secrete PTH and are the main parathyroid cell type. They are involved in primary hyperparathyroidism (adenoma) and secondary hyperparathyroidism (CKD hyperplasia).