Which substance's secretion is inhibited by low pH?

Gastrin is a hormone produced by G cells in the stomach lining that stimulates gastric acid secretion and promotes digestive processes. Low pH in the stomach indicates a highly acidic environment, which is typically a result of increased gastric acid secretion. In response to low pH, the secretion of gastrin is inhibited to prevent further acidity that could lead to mucosal injury or other digestive issues. This feedback mechanism helps maintain an optimal acid-base balance in the stomach.

In contrast, other substances like ghrelin, which stimulates appetite, cholecystokinin (CCK), which is involved in the digestion of fats and proteins, and pancreatic lipase, an enzyme that breaks down fats, do not have their secretion directly inhibited by low pH in the same manner as gastrin. Thus, gastrin's inhibition at low pH is a critical protective reflex in the digestive system, ensuring that the acidity does not reach harmful levels.