| Objective: To investigate the contents of tryptase in the ascending colon mucosa in patients with diarrhea-predominant irritable bowel syndrome (IBS-D) and the effects of tryptase on calcium mobilization of embryonic rats dorsal root ganglion neurons (DRGn) in culture.Methods: The colon mucosal culture supernatants(CMCS) were obtained from 20 IBS-D patients and 10 healthy volunteers,and the concentration of tryptase in CMCS was detected by ELISA assay. DRG neurons from embryonic SD rats were administrated as follows: group A ( the volunteer's CMCS as the control), group B (IBS-D patient's CMCS), group C (CMCS of IBS-D with Fut-175), group D (DRG neurons were pretreated with PAR-2 antagonist and then exposed to IBS-D CMCS), group E (standard tryptase 0.42ng), group F (standard tryptase 0.73ng), group G (standard tryptase 0.73ng+Fut-175), and group H (DRG neurons pretreated by PAR-2 antagonist and exposed to 0.73ng standard tryptase). Fluo-3 was used as the tracer of [Ca2+]i, and laser scanning confocal microscope was performed to conduct 90s dynamic monitoring of [Ca2+]i of DRG neurons.Results: The contents of tryptase (0.078±0.021ng/mg) in IBS-D patient's CMCS were significantly higher than that in healthy controls (0.033±0.014ng/mg) (P=0.000<0.05).The [Ca2+]i value of DRG neurons from group A to group H were 34.70±2.73,73.58±3.37, 33.53±2.13, 37.17±2.72, 36.34±0.78, 75.60±0.79, 45.13±0.83, 46.73±1.22, respectively. The values in group B and in group F were significantly higher than those in the six other groups (P<0.05,respectively), However, there was no significant difference neither between group B and group F (PBF=0.712) nor among group A, C, D, E, G and H (P>0.05).Conclusion: The contents of tryptase in the ascending colon mucosa of IBS-D patients were significantly increased. Tryptase caused the release of Ca2+ signal of DRG via PAR-2, which may involved in the pathogenesis of visceral hypersensitivity.
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