title: Carbon monoxide contributes to the constipating effects of granisetron in rat colon.
abstract: OBJECTIVE
  To investigate the mechanisms underlying the potential contribution of the heme oxygenase/carbon monoxide (HO/CO) pathway in the constipating effects of granisetron.
  
  
  METHODS
  Forin vivostudies, gastrointestinal motility was evaluated in male rats acutely treated with granisetron [25, 50, 75 μg/kg/subcutaneous (sc)], zinc protoporphyrin IX [ZnPPIX, 50 μg/kg/intraperitoneal (ip)] and hemin (50 μmol/L/kg/ip), alone or in combination. Forin vitrostudies, the contractile neurogenic response to electrical field stimulation (EFS, 3, 5, 10 Hz, 14 V, 1 ms, pulse trains lasting 10 s), as well as the contractile myogenic response to acetylcholine (ACh, 0.1-100 μmol/L) were evaluated on colon specimens incubated with granisetron (3 μmol/L, 15 min), ZnPPIX (10 μmol/L, 60 min) or CO-releasing molecule-3 (CORM-3, 100, 200, 400 μmol/L) alone or in combination. These experiments were performed under co-treatment with or without atropine (3 μmol/L, a muscarinic receptor antagonist) or NG-nitro-L-Arginine (L-NNA, 100 μmol/L, a nitric oxide synthase inhibitor).
  
  
  RESULTS
  Administration of granisetron (50, 75 μg/kg)in vivosignificantly increased the time to first defecation (P= 0.045vsvehicle-treated rats), clearly suggesting a constipating effect of this drug. Although administration of ZnPPIX or hemin alone had no effect on this gastrointestinal motility parameter, ZnPPIX co-administered with granisetron abolished the granisetron-induced constipation. On the other hand, co-administration of hemin and granisetron did not modify the increased constipation observed under granisetron alone. When administeredin vitro, granisetron alone (3 μmol/L) did not significantly modify the colon's contractile response to either EFS or ACh. Incubation with ZnPPIX alone (10 μmol/L) significantly reduced the colon's contractile response to EFS (P= 0.016) but had no effect on contractile response to ACh. Co-administration of ZnPPIX and atropine (3 μmol/L) abolished the ZnPPIX-mediated decrease in contractile response to EFS. Conversely, incubation with CORM-3 (400 μmol/L) alone increased both the contractile response to EFS at 10 Hz (10 Hz: 71.02 ± 19.16vs116.25 ± 53.70,P= 0.01) and the contractile response to ACh (100 μmol/L) (P= 0.012). Co-administration of atropine abolished the CORM-3-mediated effects on the EFS-mediated response. When granisetron was co-incubatedin vitrowith ZnPPIX, the ZnPPIX-mediated decrease in colon contractile response to EFS was lost. On the other hand, co-incubation of granisetron and CORM-3 (400 μmol/L) further increased the colon's contractile response to EFS (at 5 Hz:P= 0.007; at 10 Hz:P= 0.001) and to ACh (ACh 10 μmol/L:P= 0.001; ACh 100 μmol/L:P= 0.001) elicited by CORM-3 alone. L-NNA co-administered with granisetron and CORM-3 abolished the potentiating effect of CORM-3 on granisetron on both the EFS-induced and ACh-induced contractile response.
  
  
  CONCLUSIONS
  Taken together, findings fromin vivoandin vitrostudies suggest that the HO/CO pathway is involved in the constipating effects of granisetron.
authors.affiliation: Carmela Nacci, Maria Assunta Potenza, Valentina Leo, Monica Montagnani, Maria Antonietta De Salvia, Department of Biomedical Sciences and Human Oncology - Pharmacology Section, Medical School, University of Bari "Aldo Moro", Piazza G. Cesare, 70124 Bari, Italy.
authors.forename: Carmela
authors.initials: C
authors.lastname: Nacci
authors.affiliation: Carmela Nacci, Maria Assunta Potenza, Valentina Leo, Monica Montagnani, Maria Antonietta De Salvia, Department of Biomedical Sciences and Human Oncology - Pharmacology Section, Medical School, University of Bari "Aldo Moro", Piazza G. Cesare, 70124 Bari, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Fanelli
authors.affiliation: Carmela Nacci, Maria Assunta Potenza, Valentina Leo, Monica Montagnani, Maria Antonietta De Salvia, Department of Biomedical Sciences and Human Oncology - Pharmacology Section, Medical School, University of Bari "Aldo Moro", Piazza G. Cesare, 70124 Bari, Italy.
authors.forename: Maria Assunta
authors.initials: MA
authors.lastname: Potenza
authors.affiliation: Carmela Nacci, Maria Assunta Potenza, Valentina Leo, Monica Montagnani, Maria Antonietta De Salvia, Department of Biomedical Sciences and Human Oncology - Pharmacology Section, Medical School, University of Bari "Aldo Moro", Piazza G. Cesare, 70124 Bari, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Leo
authors.affiliation: Carmela Nacci, Maria Assunta Potenza, Valentina Leo, Monica Montagnani, Maria Antonietta De Salvia, Department of Biomedical Sciences and Human Oncology - Pharmacology Section, Medical School, University of Bari "Aldo Moro", Piazza G. Cesare, 70124 Bari, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Montagnani
authors.affiliation: Carmela Nacci, Maria Assunta Potenza, Valentina Leo, Monica Montagnani, Maria Antonietta De Salvia, Department of Biomedical Sciences and Human Oncology - Pharmacology Section, Medical School, University of Bari "Aldo Moro", Piazza G. Cesare, 70124 Bari, Italy.
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: De Salvia
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002248:Carbon Monoxide / Q000378:metabolism*; D003106:Colon / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D003248:Constipation / Q000139:chemically induced* / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control; D003672:Defecation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005769:Gastrointestinal Motility / Q000187:drug effects*; D017829:Granisetron / Q000633:toxicity*; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D006427:Hemin / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009942:Organometallic Compounds / Q000494:pharmacology; D011524:Protoporphyrins / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D012702:Serotonin Antagonists / Q000633:toxicity*; D013997:Time Factors
chemical_list: D000109:Acetylcholine; D002248:Carbon Monoxide; D017829:Granisetron; D006419:Heme Oxygenase (Decyclizing); D006427:Hemin; D009942:Organometallic Compounds; D011524:Protoporphyrins; D012702:Serotonin Antagonists; C476530:tricarbonylchloro(glycinato)ruthenium(II); C017803:zinc protoporphyrin
keywords: Carbon monoxide; Colon; Contraction; Granisetron; Heme oxygenase; Myogenic response; Neurogenic response