Inactivation of human gastric pepsin by duodenal juice

To obtain information about the destruction of pepsin by regurgitation of duodenal juice into the stomach, the effect of pH on the stability of pepsin in human gastric juice was examined in vitro. At pH below 6 no inactivation of pepsin was found by mixing duodenal juice or sodium bicarbonate with gastric juice. Similar results were obtained if glycine was added to gastric juice and the pH raised carefully by NaOH. At pH 6–8 duodenal juice irreversibly inactivated pepsin much more rapidly than did sodium bicarbonate, possibly owing to digestion of pepsin by duodenal juice enzymes.