Cellular distribution of prostanoid EP receptors mRNA in the rat gastrointestinal tract.
ABSTRACT The inhibition of PGE(2) synthesis resulting from sustained NSAIDs therapy has been linked to gastrointestinal irritations and ulceration. The multiple physiological effects of PGE(2) in the gut are mediated through the activation of four receptors termed EP(1-4). The aim of the study was to determine the precise distribution of the four prostaglandin E(2) receptors in the rat stomach, small intestine, and colon. We used non-radioactive in situ hybridization techniques on paraffin-embedded tissue. Mucous cells of the stomach and goblet cells of the small intestine and colon were found to express mRNA for all four EP subtypes. A positive hybridization signal for EP(1), EP(3), and EP(4) was detected in the parietal cells of the stomach whereas the chief cells expressed low levels of EP(1) and EP(3). The EP(1) and EP(3) receptor mRNA could also be detected in the muscularis mucosa, longitudinal muscle and enteric ganglias of the stomach and small intestine. However, close examination of the enteric ganglias indicated that most of the positive labeling was localized to the glial cells, although some neurons did express EP(3). In conclusion, we have detailed the distribution of prostanoid EP receptors in the gut at the cellular level, giving new insights to the role of prostaglandins in gastrointestinal functions.
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ABSTRACT: Lubiprostone, a chloride channel type 2 (ClC-2) activator, was thought to treat constipation by enhancing intestinal secretion. It has been associated with increased intestinal transit and delayed gastric emptying. Structurally similar to prostones with up to 54% prostaglandin E2 activity on prostaglandin E receptor 1 (EP1), lubiprostone may also exert EP1-mediated procontractile effect on intestinal smooth muscles. We investigated lubiprostone's effects on intestinal smooth muscle contractions and pyloric sphincter tone. Isolated murine small intestinal (longitudinal and circular) and pyloric tissues were mounted in organ baths with modified Krebs solution for isometric recording. Basal muscle tension and response to electrical field stimulation (EFS; 2 ms pulses/10 V/6 Hz/30 sec train) were measured with lubiprostone (10(-10)-10(-5) M) ± EP1 antagonist. Significance was established using Student t test and P < 0.05. Lubiprostone had no effect on the basal tension or EFS-induced contractions of longitudinal muscles. With circular muscles, lubiprostone caused a dose-dependent increase in EFS-induced contractions (2.11 ± 0.88 to 4.43 ± 1.38 N/g, P = 0.020) that was inhibited by pretreatment with EP1 antagonist (1.69 ± 0.70 vs. 4.43 ± 1.38 N/g, P = 0.030). Lubiprostone had no effect on circular muscle basal tension, but it induced a dose-dependent increase in pyloric basal tone (1.07 ± 0.01 to 1.97 ± 0.86 fold increase, P < 0.05) that was inhibited by EP1 antagonist. In mice, lubiprostone caused a dose-dependent and EP1-mediated increase in contractility of circular but not longitudinal small intestinal smooth muscles, and in basal tone of the pylorus. These findings suggest another mechanism for lubiprostone's observed clinical effects on gastrointestinal motility.Journal of neurogastroenterology and motility 07/2013; 19(3):312-8.
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ABSTRACT: The aims of this study were to examine the effects of doxazosin on contractile responses to 5-hydroxytryptamine (5-HT), carbachol, and histamine, and to compare them with those of prazosin, alfuzosin, and terazosin, and then characterize a pharmacological profile of the 5-HT-induced contractile response using preparations of isolated longitudinal muscle strips from the rabbit gastric body. The results from these preparations showed that the contraction response to 5-HT, but not to carbachol or histamine, was found to be dose-dependently potentiated by doxazosin and its enantiomers. The specific potentiation effect on 5-HT was not observed in the preparations that were treated with prazosin, terazosin, or alfuzosin. The contractile response to 5-HT and its potentiation by doxazosin were not affected by treatment with phenoxybenzamine. However, 5-HT-induced contraction was competitively antagonized by nefazodone (with pA2 value of 8.64 ± 0.17), and was almost completely inhibited by treatment with indomethacin. In conclusion, doxazosin, but not prazosin, alfuzosin, or terazosin, selectively potentiates 5-HT-induced contraction in the rabbit gastric body strips via an α1-adrenoceptor-independent mechanism, without chiral recognition of its enantiomers. Additionally, the contraction to 5-HT was found to be mediated via 5-HT2A receptors, and was similar to PGs synthesis in the preparations.Canadian Journal of Physiology and Pharmacology 03/2014; 92(3):197-204. · 1.56 Impact Factor
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ABSTRACT: Nowadays, aquaculture industry still confronts several disease-related problems mainly caused by viruses, bacteria and parasites. In the last decade, the use of mannan oligosaccharides (MOS) in fish production has received increased attention due to its beneficial effects on fish performance and disease resistance. This review shows the MOS use in aquaculture with a specific emphasis on the effectiveness of the several MOS forms available in the market related to disease resistance, fish nutrition and the possible mechanisms involved. Among the main beneficial effects attributed to MOS dietary supplementation, enhanced fish performance, feed efficiency and pathogen protection by potentiation of the systemic and local immune system and the reinforcement of the epithelial barrier structure and functionality are some of the most commonly demonstrated benefits. These combined effects suggest that the reinforcement of the intestinal integrity and functionality, together with the stimulation of the innate immune system, are the primary mode of action of MOS in fish. However, the supplementation strategy related to the structure of the MOS added, the correct dose and duration, as well as fish species, size and culture conditions are determinant factors to achieve improvements in health status and growth performance.Fish & Shellfish Immunology 01/2014; · 2.96 Impact Factor