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 [1-¹³C] acetic acid. The expired ¹³CO₂ 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.
Acetic Acid ; Amino Acids* ; Animals ; Arginine ; Asparagine ; Aspartic Acid ; Breath Tests ; Cysteine ; Gastric Emptying* ; Glutamic Acid ; Glutamine ; Histidine ; Lysine ; Methionine ; Phenylalanine ; Proline ; Rats ; Rats, Sprague-Dawley ; Relaxation* ; Tryptophan ; Tyrosine