The Underlying Mechanism For Anion Secretion In Rat Distal Colon

[Background&Objective] The mammalian colon is the final station of the gastrointestinaltract, where large quantities of water and electrolyte of chyme were absorbed. Another major function of the colon is secretion of electrolytes, which is balanced by absorption. Secretion and absorption are controlled by endocrine, paracrine, autocrine, immunologic, and neuronal stimuli. Compounds that are present in the body, such as hormones, immunologic factors, neurotransmitters and brain-gut peptide,may modulate secretion and absorption via second messengers Ca²⁺, cGMP, or cAMP. Electrogenic Cl^- secretion is the fundamental means of intestinal mucosal surface hydration as a primitive defence mechanism which can prevent the mucosa from noxious stimuli and several human diseases including secretion diarrhea and cystic fibrosis result from its defective regulation. HCO₃^-, similar to Cl^-, is also an important component of normal colonic fluid and its secretion occurs all over the alimentary tract. Furthermore, colonic HCO₃^- secretion significantly reduces exposure of epithelium to H₂S through conversion to anionic sulfide and may represent a functional detoxification mechanism. Some H₂S-induced oxidative changes closely resembled the impairment of β-oxidation observed in ulcer colonitis patients' colonocytes. Also, H₂S generation rates and concentration in UC, colorectal cancer feces were significantly greater than that in normal fecal samples. Some clinic studies indicated faecal pH and HCO3" were significantly reduced in UC versus controls. According to those findings, we believed abnormal HCO₃^- secretion may be one of the environmental factors leading to IBD, UC and CRC . There were many studies involved in anion transport in rat distal colon but few of them were concerned on the segmental difference. The aim of the present study is to investigate the distinct effects and mechanism of elevating intracellular cAMP caused by FSK on the ion transports in different segments of rat distal colon.[Material & Methods]Healthy adult male SD rats were used. Segments of distal colon about...