Papain reduces gastric acid secretion induced by histamine and other secretagogues in anesthetized rats.

We studied the effect of papain on rats' gastric acid secretion and found that: 1. Feeding of latex of unripe papaya fruit significantly reduced gastric acid secretion induced by methacholine; 2. Feeding of crystalline papain in doses of 3.2 mg/kg reduced gastric acid secretion induced by histamine, methacholine and tetragastrin; 3. The reduction of gastric acid secretion was observed as early as 2 hours after papain feeding, lasted up to 48 hours, and waned within 96 hours; 4. Intraperitoneal injection of papain had no effect on acid secretion. These results led us to believe tha the effect of papain on gastric acid secretion is a local one acting directly on the gastric mucosa, and this local effect of a single dose of papain is reversible, causing no permanent damage to the mucosa.