Changes in total pepsin activity and pepsinogen I in human sera under stimulation and inhibition of gastric acid secretion.

The levels of total pepsin activity and pepsinogen I in sera were first studied in 10 healthy volunteers undergoing stimulation of gastric acid secretion at random on 4 different days with a) a maximum dose (6 micrograms/kg) of pentagastrin, b) ranitidine injection 5 minutes before maximal pentagastrin stimulation, c) ranitidine injection 1 hr before maximal pentagastrin stimulation, or d) sham feeding. In a further 10 healthy volunteers the levels of total pepsin activity and pepsinogen I were studied over 5 days by short-term oral intake of ranitidine. The total pepsin activity and pepsinogen I increased significantly in the sera after maximum-dose pentagastrin, but not after sham feeding. The increase could be completely prevented by ranitidine given only 1 hour before pentagastrin stimulation. The total pepsin activity and pepsinogen I decreased significantly after brief oral intake of ranitidine. It can be concluded that the measurement of total pepsin activity and pepsinogen I in the sera could serve as a rough parameter for testing the effectiveness of potential agents inhibiting gastric secretion.