¹³C-Acetic Acid Is More Sensitive Than ¹³C-Octanoic Acid for Evaluating Gastric Emptying of Liquid Enteral Nutrient Formula by Breath Test in Conscious Rats

Abstract

Breath test using ¹³C-labeled compound has been used as a convenient method to evaluate gastric emptying. ¹³C-Labeled acetic acid or octanoic acid has been used in clinic. However, there is few report comparing two compounds. This study aimed to compare ¹³C-acetic acid and ¹³C-octanoic acid in newly-constituted breath test for monitoring gastric emptying in conscious rats. After fasting, rats were orally administered Racol (liquid enteral nutrient formula) containing ¹³C-labeled compound (same molar of ¹³C-acetic acid or ¹³C-octanoic acid) and housed in a chamber. The expired air in the chamber was collected in a breath-sampling bag using a tube and aspiration pump. The level of ¹³CO₂ in the expired air was measured using an infrared spectrometer at appropriate intervals for 120 min. Expired ¹³CO₂ air from ¹³C-acetic acid changed at significantly higher levels than that from ¹³C-octanoic acid. C_max and AUC_{120 min} values of expired ¹³CO₂ from ¹³C-acetic acid were significantly higher than those from ¹³C-octanoic acid, but T_max was not different between them. These results show that ¹³C-acetic acid is more sensitive for monitoring gastric emptying than ¹³C-octanoic acid in liquid test meal although both acids clearly monitored gastric emptying.