Composition of the Alkaline Component of Human Gastric Juice: Effect of Swallowed Saliva and Duodeno-Gastric Reflux

Abstract

Five patients (four with vitiligo and one with pernicious anaemia) were subjected to the histamine infusion test; there were achlorhydric while the remaining two secreted quite small amounts of acid. [Na+],[Cl-)and[alkali]were determined in the alkaline gastric juice samples (pH greater than 7.0). In order to assess the contribution of swallowed saliva the histamine test was done twice in each patient: (A) with precautions to prevent swallowing of saliva; and (B) with the patient allowed to swallow saliva freely. In each sample reflux of duodenal juice was estimated so that its contribution to the alkaline gastric aspirate could be assessed. Such reflex was absent in one patient, negligible in another, while in the remaining three patients the mean pyloric reflux amounted to no more than 8% of the observed volume. Swallowed saliva had diluting effect on [Na+] and [Cl-] but raised K+ concentration in the alkaline gastric aspirate. The comparison of alkaline gastric juice, free to an appreciable extent of salivary contamination, was shown to be relatively constant. The results are consistent with the two-component hypothesis of gastric secretion.

Measuring pH and Buffer Capacity in Fluids Aspirated from the Fasted Upper Gastrointestinal Tract of Healthy Adults

“…Bicarbonate concentrations in the acid-suppressed stomach using the carbon dioxide partial pressure and pH (pCO 2 /pH) method (which is based on the Henderson-Hasselbalch equation and in which the total concentration of bicarbonates is considered to be the sum of carbon dioxide and free bicarbonates) have been reported to range from 1 to 20mM. (9,10) In the fasted small intestine, on the other hand, the pH is considered to be mainly controlled by bicarbonates, which are secreted by the pancreas and the enterocytes and are also present in the bile. (11)(12)(13)(14) Using the pCO 2 /pH method, the bicarbonate concentration in the upper intestine (duodenum and jejunum) of fasted adults has been measured to range between 2 and 20 mM, and the influx of hydrochloric acid into the upper small intestine has been shown to result in a significant increase in bicarbonate secretion rates.…”