Table 4

 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 patientsControlsATD v placebo (p value)
t = 8:00t = 15:00t = 8:00t = 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)ATD65.6 (3.0)23.1 (2.4)68.4 (2.7)26.7 (3.1)<0.0001
Placebo62.8 (2.0)91.0 (6.0)65.2 (2.1)100 (5.7)
Tryptophan/ΣLNAAs (×100)ATD11.9 (2.5)2.30 (1.0)12.1 (2.6)2.30 (0.7)<0.0001
Placebo11.4 (2.4)9.70 (2.1)11.4 (2.0)10.3 (2.9)
Platelet 5-HT (nmol/109 platelets)ATD4.40 (0.4)4.80 (0.5)5.70 (0.7)5.80 (0.8)0.78
Placebo4.30 (0.6)4.50 (0.6)5.20 (0.7)5.40 (0.8)
ppp 5-HIAA (nmol/l)ATD28.9 (1.6)15.6 (1.0)30.9 (1.1)16.1 (0.8)<0.0001
Placebo28.9 (1.1)29.4 (1.2)29.8 (1.3)31.6 (1.8)
ppp 5-HT (nmol/l)ATD9.80 (1.6)10.7 (1.4)9.20 (1.5)7.90 (1.1)0.25
Placebo10.7 (1.7)10.8 (1.7)9.01 (1.2)11.9 (1.5)
5-HT turnoverATD3.80 (0.5)2.34 (0.6)3.98 (0.5)2.68 (0.5)<0.01
Placebo3.48 (0.5)3.37 (0.6)3.97 (0.5)3.63 (0.6)