Relation Between Stimulatory Effect on Gastric Acid Secretion and Antral Absorption of Chemical Compounds

Abstract

Five Heidenhain and two Pavlov pouch dogs were used to study the influence of acidity variations within the isolated antrum on absorption and on gastrin release by one ionizable (choline) and two unionizable compounds (ethanol, n-propanol). Absorption of ethanol and n-propanol was determined by measuring the concentration of the alcohols in the portal blood, in peripheral venous blood, and in the antrum. The constants of absorption were identical for the two alcohols at pH 7. Even though gastrin release by both alcohols was inhibited at low pH levels (pH < 2), the constants remained the same at pH 3 and pH 1 for ethanol and were only slightly lowered for n-propanol (instillation of 10% v/v solutions). Antral perfusion at various pH levels with graded concentrations (2, 4, and 8% solutions) of choline showed a significant increase of free plasma choline at pH 7 and a slight increase at pH 5 with 8% solutions, but no increase with 1–4% choline solutions of pH 7, 5, 3, or 1. Acid output during choline application was already inhibited at pH 5. Intravenous infusion of graded amounts of choline (0.1–0.8 g/hr) stimulated acid output of the fundic pouches at a threshold dose of 0.4 g/hr. Combined administration of the intravenous threshold dose and graded antral concentrations demonstrated a synergistic action on the parietal cells between released gastrin and increased plasma choline. The results suggest that more than one mechanism may be involved in inhibition of gastrin release by acid.

Key-words:

• Absorption
• animal experiments
• alcohol, ethyl
• alcohol, propyl
• choline
• gastric juice
• gastrin
• portal veins