Content area
Abstract
Introduction: Despite toxicological concerns, endogenous hydrogen sulphide (H2S) has physiological roles such as anti-inflammatory effects, namely in the intestine. But, high intestinal concentrations of H2S have also been considered a trigger for the development of inflammatory bowel disease (IBD). However, there is still no data on the action of H2S on intestinal motility in GI diseases, such as IBD. TNBS-induced colitis is the most frequently used experimental model of IBD in rats, but is associated with pain and discomfort.
Aims: To further refine the TNBS-induced model of colitis in rats, to increase welfare and reduce the percentage of rats developing severe colitis. Also, to understand the role of H2S on colonic reactivity in this experimental model of IBD.
Methods: Protocols were approved by the institutional and national Animal Welfare Body. For induction of TNBS-induced colitis, male Wistar rats (16-18 weeks old; n=12) received a 30% ethanolic solution of TNBS (15mg/rat; 250 μL) rectally instilled. Pain relief and colonic motility were assured with metoclopramide (1mg/Kg, PO), and tramadol (20mg/kg, PO, once) and paracetamol (500 mg/kg, PO, SID). Animals were daily monitored for body weight, food and water intake, fecal peletts, and wellbeing. After 7 days, TNBS and control rats were euthanized by decapitation, the colon was excised and attributed a macroscopic score (MaS). Segments of the proximal (PC), middle (MC) and distal (DC) colon were mounted in organ baths and the effect of the H2S donor, NaHS was tested over AChinduced precontraction, on ACh-induced contraction, and directly on basal resting tone.
Results:According to the MaS, TNBS-induced colitis coursed with 4 animals with mild and 8 with moderate colitis (no rats developing severe colitis). TNBS-induced rats showed a similar pattern in all parameters analysed, although different from controls. The Welfare Score correlated with MaS. NaHS caused similar concentration-dependent relaxation of PC, MC and DC precontracted with ACh in control and TNBS-induced rats. In control rats, but not in TNBS-induced rats, NaHS decreased the contractile response to Ach. NaHS caused a concentration-dependent decrease in the basal resting tone of the PC and altered the pattern of spontaneous contractions in controls and TNBS-induced rats.
Conclusions:It was possible to refine the rat TNBS-induced model of IBD. In control conditions, NaHS relaxes the pre-contracted colon and attenuates ACh-mediated contractions. The mechanism underlying this effect is probably different and selectively compromised in the TNBS-induced rat, but further studies are needed to clarify these results.
