Biochemical parameters at t = 8:00 and t = 15:00 (mean (SEM)) during acute tryptophan depletion (ATD) and placebo, in the diarrhoea predominant irritable bowel syndrome (d-IBS) patients and control subjects
| d-IBS patients | Controls | ATD v placebo (p value) | ||||
|---|---|---|---|---|---|---|
| t = 8:00 | t = 15:00 | t = 8:00 | t = 15:00 | |||
| 5-HT, 5-hydroxytryptamine (serotonin); ppp, platelet poor plasma; 5-HIAA, 5-hydroyindole acetic acid; ΣLNAAs, large neutral amino acids (sum of tyrosine, valine, leucine, isoleucine, and phenylalanine). | ||||||
| Tryptophan (μmol/l) | ATD | 65.6 (3.0) | 23.1 (2.4) | 68.4 (2.7) | 26.7 (3.1) | <0.0001 |
| Placebo | 62.8 (2.0) | 91.0 (6.0) | 65.2 (2.1) | 100 (5.7) | ||
| Tryptophan/ΣLNAAs (×100) | ATD | 11.9 (2.5) | 2.30 (1.0) | 12.1 (2.6) | 2.30 (0.7) | <0.0001 |
| Placebo | 11.4 (2.4) | 9.70 (2.1) | 11.4 (2.0) | 10.3 (2.9) | ||
| Platelet 5-HT (nmol/109 platelets) | ATD | 4.40 (0.4) | 4.80 (0.5) | 5.70 (0.7) | 5.80 (0.8) | 0.78 |
| Placebo | 4.30 (0.6) | 4.50 (0.6) | 5.20 (0.7) | 5.40 (0.8) | ||
| ppp 5-HIAA (nmol/l) | ATD | 28.9 (1.6) | 15.6 (1.0) | 30.9 (1.1) | 16.1 (0.8) | <0.0001 |
| Placebo | 28.9 (1.1) | 29.4 (1.2) | 29.8 (1.3) | 31.6 (1.8) | ||
| ppp 5-HT (nmol/l) | ATD | 9.80 (1.6) | 10.7 (1.4) | 9.20 (1.5) | 7.90 (1.1) | 0.25 |
| Placebo | 10.7 (1.7) | 10.8 (1.7) | 9.01 (1.2) | 11.9 (1.5) | ||
| 5-HT turnover | ATD | 3.80 (0.5) | 2.34 (0.6) | 3.98 (0.5) | 2.68 (0.5) | <0.01 |
| Placebo | 3.48 (0.5) | 3.37 (0.6) | 3.97 (0.5) | 3.63 (0.6) | ||