Effects of straight alkyl chain, extra hydroxylated alkyl chain and branched chain amino acids on gastric emptying evaluated using a non-invasive breath test in conscious rats

Aim: Some amino acids been known to influence gastric emptying. Thus we have evaluated the effects of straight alkyl chain, extra hydroxylated alkyl chain and branched chain amino acids on gastric emptying. Materials and Methods: Gastric emptying was evaluated in rats after feeding with Racol (nutrient formulae) containing [1-(13)C] acetic acid. Using a breath test, the content of (13)CO(2) in their expired air was measured by infrared analyzers. Rats were orally administered with test amino acids, while control rats were administered orally with distilled water. Results: The expired (13)CO(2) content in the expired air increased with time, peaked after about 30 min and decreased thereafter. Among the amino acids having an alkyl chain, l-serine, l-alanine and l-glycine, significantly decreased the (13)CO(2) content and Cmax, and delayed Tmax, suggesting inhibition and delay of gastric emptying. AUC(120 min) values of l-alanine and l-glycine also decreased significantly. l-Threonine significantly decreased (13)CO(2) content and delayed Tmax, but had no influence on Cmax and AUC(120 min) values, suggesting a delay of gastric emptying. l-Isoleucine and l-leucine and l-valine significantly decreased (13)CO(2) content, suggesting inhibition of the gastric emptying, but Cmax, Tmax and AUC(120 min) values were not significantly affected. Conclusion: The results show that the amino acids used in the present study had different effects on gastric emptying. Moreover, it was found that inhibition and delay of gastric emptying were clearly classifiable by analyzing the change in (13)CO(2) content of the expired air and the Cmax, Tmax and AUC(120 min) values.