Carbon monoxide contributes to the constipating effects of granisetron in rat colon

World J Gastroenterol. 2016 Nov 14;22(42):9333-9345. doi: 10.3748/wjg.v22.i42.9333.


Aim: To investigate the mechanisms underlying the potential contribution of the heme oxygenase/carbon monoxide (HO/CO) pathway in the constipating effects of granisetron.

Methods: For in vivo studies, 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. For in vitro studies, 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 vivo significantly increased the time to first defecation (P = 0.045 vs vehicle-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 administered in 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 ± 19.16 vs 116.25 ± 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-incubated in vitro with 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.

Conclusion: Taken together, findings from in vivo and in vitro studies suggest that the HO/CO pathway is involved in the constipating effects of granisetron.

Keywords: Carbon monoxide; Colon; Contraction; Granisetron; Heme oxygenase; Myogenic response; Neurogenic response.

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Carbon Monoxide / metabolism*
  • Colon / drug effects*
  • Colon / metabolism
  • Colon / physiopathology
  • Constipation / chemically induced*
  • Constipation / metabolism
  • Constipation / physiopathology
  • Constipation / prevention & control
  • Defecation / drug effects*
  • Dose-Response Relationship, Drug
  • Electric Stimulation
  • Gastrointestinal Motility / drug effects*
  • Granisetron / toxicity*
  • Heme Oxygenase (Decyclizing) / metabolism
  • Hemin / pharmacology
  • In Vitro Techniques
  • Male
  • Organometallic Compounds / pharmacology
  • Protoporphyrins / pharmacology
  • Rats, Sprague-Dawley
  • Serotonin Antagonists / toxicity*
  • Time Factors


  • Organometallic Compounds
  • Protoporphyrins
  • Serotonin Antagonists
  • tricarbonylchloro(glycinato)ruthenium(II)
  • zinc protoporphyrin
  • Hemin
  • Carbon Monoxide
  • Heme Oxygenase (Decyclizing)
  • Acetylcholine
  • Granisetron