Modulation in Natriuretic Peptides System in Experimental Colitis in Rats

Background: Renin-angiotensin system is involved in the pathophysiology of colonic inflammation. However, there are a few reports about modulation of natriuretic peptide system. Aims: This study investigates whether a local atrial natriuretic peptide (ANP) system exists in rat colon and whether ANP plays a role in the regulation of colonic motility in experimental colitis rat model. Methods: Experimental colitis was induced by an intake of 5 % dextran sulfate sodium (DSS) dissolved in tap water for 7 days. After rats were killed, plasma hormone concentrations and mRNAs for natriuretic peptide system were measured. Functional analysis of colonic motility in response to ANP was performed using taenia coli. Results: DSS-treated colon showed an increased necrosis with massive infiltration of inflammatory cells. The colonic natriuretic peptide receptor-A mRNA level and particulate guanylyl cyclase activity in response to ANP from colonic tissue membranes were higher, and the mRNA levels of ANP and natriuretic peptide receptor-B were lower in DSS-treated rats than in control rats. ANP decreased the frequency of basal motility in a dose-dependent manner but did not change the amplitude. The inhibitory responses of frequency of basal motility to ANP and 8-bromo-cGMP were enhanced in DSS-treated rat colon. Conclusion: In conclusion, augmentation of inhibitory effect on basal motility by ANP in experimental colitis may be due an increased expression of colonic natriuretic peptide receptor-A mRNA. These data suggest that local natriuretic peptide system is partly involved in the pathophysiology of experimental colitis.