OBSERVATIONS ON THE HUMAN GASTRO-DUODENAL SECRETIONS WITH SPECIAL REFERENCE TO THE ACTION OF HISTAMINE

¹ The Department of Physiology, University of Edinburgh

1. The overnight juice or "residuum" may be described as follows. Amount 52 cc. ; active HCl, 0.150 grm. % ; pepsin, 0.369 grm. % ; mucus and occasionally bile. The analysis of the overnight juice gives no information regarding the secretory state of the stomach ; the amount of the juice depends on the tonie of the stomach wall and its holding capacity.

2. The basal or fasting juice is as follows. Amount 12 cc. (per 10 minutes); active HCl 0.185 grm. % ; pepsin, 0.544 grm. % ; bile, etc., should be absent. The basal acidity in the majority of cases is low but individuals may show considerable variation. The analysis of the basal juice is of great importance, especially the estimation of the acid output per unit time, as it furnishes the only reliable control to further experimental observations.

3. The gastric response. Histamine increases the rate of secretion, and the amount of acid and pepsin. The acid is secreted at a maximum rate for the period of response induced, while the stomach seeks to establish an optimum concentration of acid. The amount of fluid secreted is governed by the necessity of producing an optimum concentration from the acid output. The actual response in each case is therefore governed by the level of the basal output. The average acidity is 0.346 grm. % HCl ; this and actually lower figures in individuals are obtainable in the absence of duodenal regurgitation.

In short the acidity of the freshly secreted juice is seldom as high as 0.5 grm.% HCl, the commonly accepted figure.

The pepsin increase is irregular, and apparently unrelated to either acidity or amount of juice.

4. The influence of atropine. The local application of atropine in doses up to 0.0026 grm. of the sulphate for a period of ten minutes is ineffective in inhibiting the histamine response. The subcutaneous injection of 0.00065 grm. atropine sulphate has also no influence. Histamine must therefore act directly on the secreting cells.

5. The duodenal rcsponse. Histamine has no direct action on the duodenal, pancreatic, or biliary secretions, but under normal conditions it stimulates these secretions indirectly when the acid of the gastric response escapes into the duodenium.

6. Histamine and the alveolar CO₂. Both a rise and a fall of alveolar CO₂ pressures may be obtained after histamine. These changes nmay be supposed to result from a preponderating secretion of acid and of alkali respectively, although the evidence available cannot be considered as conclusive.

We wish to acknoweledge our indebtedness to those students of this University who have volunteered for the experiments described in this paper.

The expenses incurred have been defrayed by grants from the Carnegie Trust and from the Earl of Moray Fund for the promotion of Research in the University ot Edinburgh.