title: Relaxin depresses small bowel motility through a nitric oxide-mediated mechanism. Studies in mice.
abstract: Gastrointestinal motility is reduced and the incidence of functional gastrointestinal disorders is increased in pregnancy, possibly due to hormonal influences. This study aims to clarify whether the hormone relaxin, which attains high circulating levels during pregnancy and has a nitric oxide-mediated relaxant action on vascular and uterine smooth muscle, also reduces bowel motility and, if it does, whether nitric oxide is involved. Female mice in proestrous or estrous were treated for 18 h with relaxin (1 microg s.c.) or vehicle (controls). Isolated ileal preparations from both groups were used to record contractile activity, either basal or after acute administration of relaxin (5 x 10(-8) M). Drugs inhibiting nitric oxide biosynthesis or neurotransmission were used in combination with relaxin. Expression of nitric oxide synthase isoforms by the ileum was assessed by immunocytochemistry and Western blot analysis. Relaxin caused a clear-cut decay of muscle tension and a reduction in amplitude of spontaneous contractions upon either chronic administration to mice or acute addition to isolated ileal preparations. These effects were significantly blunted by N(G)-nitro-L-arginine, but not by the neural blockers we used. Moreover, relaxin increased the expression of nitric oxide synthases II and III, but not synthase I. Relaxin markedly inhibits ileal motility in mice by exerting a direct action on smooth muscle through the activation of intrinsic nitric oxide biosynthesis.
authors.affiliation: Department of Anatomy, Histology, and Forensic Medicine, University of Florence, Florence, Italy. bani@unifi.it
authors.forename: Daniele
authors.initials: D
authors.lastname: Bani
authors.forename: Maria Catarina
authors.initials: MC
authors.lastname: Baccari
authors.forename: Silvia
authors.initials: S
authors.lastname: Quattrone
authors.forename: Silvia
authors.initials: S
authors.lastname: Nistri
authors.forename: Franco
authors.initials: F
authors.lastname: Calamai
authors.forename: Mario
authors.initials: M
authors.lastname: Bigazzi
authors.forename: Tatiana
authors.initials: T
authors.lastname: Bani Sacchi
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D015153:Blotting, Western; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects*; D007082:Ileum / Q000201:enzymology / Q000502:physiology; D007150:Immunohistochemistry; D051379:Mice; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D019335:Nitroarginine / Q000494:pharmacology; D011247:Pregnancy; D012065:Relaxin / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology; D020960:omega-Conotoxins / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D018727:Muscarinic Antagonists; D020960:omega-Conotoxins; D019335:Nitroarginine; D009569:Nitric Oxide; D013779:Tetrodotoxin; D001285:Atropine; D012065:Relaxin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse