Correlation Between Gastric Emptying and Gastric Adaptive Relaxation Influenced by Amino Acids

Background/Aims Amino acids have many physiological activities. We report the correlation between gastric emptying and gastric adaptive relaxation using tryptophan and amino acids with a straight alkyl chain, hydroxylated chain, and branched chain. Here we sought to further clarify the correlation between gastric emptying and gastric adaptive relaxation by using other amino acids. Methods In Sprague-Dawley rats, gastric emptying was evaluated by a breath test using [1-C-13] acetic acid. The expired (CO2)-C-13 pattern, T-max, C-max, and AUC(120min) values were used as evaluation items. Gastric adaptive relaxation was evaluated in a barostat experiment. Individual amino acids (1 g/kg) were administered orally 30 minutes before each breath test or barostat test. Results L-phenylalanine and L-tyrosine did not influence gastric emptying. All other amino acids, ie, L-proline, L-histidine, L-cysteine, L-Methionine, L-aspartic acid, L-glutamic acid, L-asparagine, L-arginine, L-glutamine, and L-lysine significantly delayed and inhibited gastric emptying. L-Cysteine and L-aspartic acid significantly enhanced and L-methionine and L-glutamine significantly inhibited gastric adaptive relaxation. L-Phenylalanine moved the balloon toward the antrum, suggesting strong contraction of the fundus. T-max showed a significant positive correlation (r = 0.709), and C-max and AUC(120min) each showed negative correlations (r = 0.613 and 0.667, respectively) with gastric adaptive relaxation. Conclusion From the above findings, it was found that a close correlation exists between gastric emptying and adaptive relaxation, suggesting that enhanced gastric adaptive relaxation inhibits gastric emptying.