Calcium [¹³C]carbonate breath test for quantitative measurement of total gastric acid in rats

Abstract

Objective. A traditional measurement of gastric acid, involving nasogastric intubation of stomach and acid suction, has been suggested as a gold standard. However, this causes the patient discomfort and cost increase, and is ‘time-consuming’. Material and methods. A calcium [¹³C]carbonate (Ca¹³CO₃) breath test was carried out in rats without or with concomitant drugs omeprazole (OMP) and pentagastrin (PG) known as an inhibitor and an inducer of acid, respectively. This test was aimed at evaluating a correlation between the breath response and the total amount of gastric acid. To search for an absorption pathway of ¹³CO₂ gas produced by the reaction of Ca¹³CO₃ with hydrochloric acid in the stomach of rats, we compared the breath responses after intra-gastric administration of ¹³CO₂ gas and sodium [¹³C]bicarbonate (NaH¹³CO₃). Results. A linear relationship of the breath parameter (breath-C_max) with the dose of Ca¹³CO₃ was obtained in the range of 4–200 µmol/kg. However, theses parameters were saturated at >200 µmol/kg. The direct correlation between the breath-C_max and the total amount of gastric acid in rats with or without OMPs or PG (r = 0.994) demonstrated that the change in breath response is an accurate or sensitive indicator of the total amount of gastric acid. ¹³CO₂ gas generated in the rat stomach was likely to diffuse across the stomach wall as ¹³CO₂ gas directly into the blood plasma. Conclusions. The present study showed that Ca¹³CO₃ breath test is a good tool to accurately predict the total amount of gastric acid.

Key Words::

• breath test
• Ca¹³CO3
• calcium [¹³C]carbonate
• gastric acid
• proton pump inhibitor

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.