Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The action of highly purified Clostridium difficile toxin A was studied in the jejunum of rats in vivo. C. difficile toxin A reversed dose-dependently net fluid absorption into net fluid secretion, accompanied by an increase in prostaglandin E2 but not 5-hydroxytryptamine output into the gut lumen. Accordingly, indomethacin but not the 5-hydroxytryptamine receptor antagonists ketanserin plus tropisetron were able to inhibit toxin A-induced fluid secretion. Atropine and hexamethonium were without effect on the action of toxin A, such excluding a nervous mechanism. The cyclic nucleotides cyclic AMP and cyclic GMP appear not to be involved in the mediation of the secretory response. The reduced cyclic GMP levels are most likely the result of a complete destruction of the villus membranes, where the guanylate cyclase is located. Histological studies revealed massive damage to intestinal villi, whereas the majority of the crypts seem to be unaffected. In conclusion, toxin A-induced intestinal fluid secretion appears to be caused mainly by severe mucosal damage. PGE2-release may be the consequence of the inflammation accompanying this damage. The mechanism seems to be completely different to those of cholera toxin or Escherichia coli heat stable enterotoxin.
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PMID:Effects of purified Clostridium difficile toxin A in the small intestine of the rat in vivo. 790 88

We investigated the effect of sodium nitroprusside (SNP), a donor of nitric oxide, on the formation of platelet-activating factor (PAF) and uterine contractility in mouse uterine horns from mice treated with estrogen. Because the major pathway of PAF synthesis is the remodeling pathway in uterine tissue, we evaluated the incorporation of 14C-acetate into PAF-like molecules. Our results showed that SNP (100-300 mumol/L) caused a transient increase in the synthesis of PAF, which remained cell-associated. The addition of SNP (100-300 mumol/L) to a mouse uterine horn in an isolated organ bath preparation evoked a transient increase in contractility, which was inhibited by hemoglobin (2 micrograms/mL), a nitric oxide scavenger, but not by methylene blue (10 mumol/L), a guanylate cyclase inhibitor. The pharmacological characteristics of the contractions evoked by SNP resembled those evoked after mast cell activation, in that they were blocked by ritodrine (a beta 2 adrenergic agonist, 0.1 mumol/L); indomethacin (a cyclooxygenase inhibitor, 10 mumol/L); ketotifen (a mast cell stabilizer, 1.0 mumol/L); cromolyn sodium (a mast cell stabilizer, 100 mumol/L); pyrilamine (an H1 antagonist, 10 mumol/L); and ketanserine (5HT2 antagonist, 0.1 mumol/L). These data demonstrate that nitric oxide generated from SNP stimulated the synthesis of PAF and evoked contractility in uterine horns from mice treated with estrogen. This result suggests the possibility that these tissue conditions might be favorable for the generation of peroxynitrites, possible mediators of both effects. It is also shown that the contractility evoked by the addition of SNP was not due to production of PAF, because its antagonist, WEB 2086 (10-30 mumol/L, a concentration that blocked contractions evoked by PAF 1 nmol/L), had no effect on the SNP-evoked contractions.
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PMID:Nitroprusside stimulates contractility and the synthesis of 14C-acetylated PAF-like substances in estrogen primed-mouse uterine horns. 1036 96

Nitric oxide synthase (NOS) positive neurons are located in most brain areas related to defensive reactions, including the dorsolateral periaqueductal grey (dlPAG). NOS inhibitors injected into this structure induce anxiolytic-like responses whereas NO donors promote flight reactions. Intra-dlPAG administration of carboxy-PTIO, a NO scavenger, or ODQ, a soluble guanylate cyclase inhibitor, produced anxiolytic-like effects on rats exposed to the elevated plus-maze (EPM). A double-staining experiment using NADPHd histochemistry and c-Fos immunohistochemistry in rats exposed to a cat or to the EPM showed increased activation of NO producing neurons in the dlPAG, paraventricular and lateral nuclei of hypothalamus and dorsal raphe nucleus. Cat exposure also increased activation of NOS neurons in the medial amygdala, dorsal pre-mammillary nucleus and bed nucleus of stria terminalis. Local infusion into the dlPAG of a glutamate NMDA-receptor antagonist (AP7) or a benzodiazepine agonist (midazolam) completely prevented the flight reactions induced by intra-dlPAG administration of SIN-1, a NO donor. The responses were also inhibited by the 5-HT2A/C agonist DOI but not by a 5-HT1A agonist. These results suggest a modulatory role for NO on brain areas related to defensive reactions, probably by interacting with glutamate, serotonin and/or GABA-mediated neurotransmission.
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PMID:Role of nitric oxide in brain regions related to defensive reactions. 1609 96

New therapies are being developed for irritable bowel syndrome (IBS). These advances are based on understanding pathophysiology or the development of medications with greater selectivity in classes of agents with known efficacy. Prucalopride, the newest European Medicines Agency-approved 5-hydroxytryptamine receptor 4 (5-HT(4)) agonist, is effective in the treatment of chronic constipation with improved cardiovascular safety relative to older 5-HT(4) drugs; similarly, ramosetron, the 5-hydroxytryptamine receptor 3 (5-HT(3)) antagonist, appears efficacious in diarrhea-predominant IBS. Secretagogues with different mechanisms of action target apical domains in enterocytes that are involved in chloride secretion, such as chloride channels, the cystic fibrosis transmembrane regulator, and guanylate cyclase C. As a class, such secretagogues have high efficacy and safety for constipation. With more data obtained from phase 2 and 3 trials, we expect other classes of medications, including bile acid modulators, anti-inflammatory agents, visceral analgesics, and newer centrally acting agents to be efficacious and enter the armamentarium for the treatment of IBS in the future.
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PMID:Emerging pharmacologic therapies for irritable bowel syndrome. 2069 41

Constipation is a common medical problem and when standard laxatives fail it can be difficult to treat. Different aetiologies require tailored therapeutic approaches. Simple constipation may only require dietary manipulation while severe neurological or slow transit constipation may need pharmacologic intervention. Recently new drug therapies have been introduced. PubMed and Ovid were searched for reviews, systematic reviews and meta-analysis published since 2003 using the terms: constipation, prucalopride, linaclotide and lubiprostone. This review summarizes potential novel therapies identified as effective in the management of chronic constipation. Prucalopride is a selective 5-hydroxytryptamine receptor agonist. The prucalopride study was in patients, largely women with idiopathic constipation showed improved spontaneous complete bowel movement (SCBM) at a dose of 2 mg a day with few adverse events reported. Linaclotide is a 14-amino acid peptide guanylate cyclase-C agonist. The linaclotide study was carried out in patients with irritable bowel syndrome, constipation group (IBS-C). There was significant improvement of bowel evacuation and symptom resolution in patients on the active treatment arm. Lubiprostone activates type-2 chloride channels, increasing intestinal fluid secretion. In the trials of this drug, the lubiprostone arms had a greater mean number of SCBM. The novel therapies, prucalopride, lubiprostone, and linaclotide had very different modes of action yet, all three have been shown to be efficacious and safe in the treatment dose for constipation.
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PMID:Novel therapies for constipation. 2436 15