title: Sodium nitroprusside regulates the relaxation of the longitudinal muscle in the gut.
abstract: Nitric oxide (NO) has been shown to mediate nonadrenergic-noncholinergic relaxation in gastrointestinal (GI) smooth muscle cells. As GI smooth muscles relaxations are partly dependent on NO, we decided to investigate the effect of sodium nitroprusside (SNP) on the longitudinal muscle contraction of the isolated guinea pig ileum. Increasing concentrations of SNP (10(-10)M, 10(-9)M, 10(-8)M, 10(-7)M, 10(-6)M and 10(-5)M) reduced ileum contractions stimulated by electrical stimulation (ES) (8-76%; p < 0.05) and by acetylcholine (Ach) (23-62%; p < 0.05) significantly and in a concentration-dependent manner. Furthermore, treatment with an inhibitor of the soluble guanylate cyclase, methylene blue (10 mM), antagonized significantly the relaxing effect of SNP (0-39%; p < 0.05, p < 0.01, p < 0.001 for ES- and 4-27%; p < 0.05 for Ach-induced contractions). The results show that treatment with 1 microM manganese-containing superoxide dismutase (MnSOD) and 10 microM L-arginine (L-arg) caused a significant decrease in SNP induced relaxations (6-55%; p < 0.05, p < 0.001 and 2-46%; p < 0.05, p < 0.01 for ES- and 15-28%; p < 0.05, p < 0.01, p < 0.001 and 12-32%; p < 0.05, p < 0.01 for Ach-induced contractions, respectively). In conclusion, our data suggest that SNP, which releases NO, is able to depress longitudinal muscle contraction of the isolated guinea pig ileum, suggesting that exogenous application of NO inhibits intestinal contractions of smooth muscle cells and that cGMP mediates the response to NO. In addition, MnSOD and L-arg decreased the relaxing effect of SNP on the isolated ileum of the guinea pig.
authors.affiliation: Laboratory for Molecular Biology and Endocrinology, Institute Vinca, P.O. Box 522, 11001 Belgrade, Serbia. sradivojsa@rt270.vin.bg.ac.yu
authors.forename: S N
authors.initials: SN
authors.lastname: Tepavcević
authors.forename: E R
authors.initials: ER
authors.lastname: Isenović
authors.forename: V M
authors.initials: VM
authors.lastname: Varagić
authors.forename: S R
authors.initials: SR
authors.lastname: Milovanović
mesh_terms: D000818:Animals; D001120:Arginine / Q000494:pharmacology; D005260:Female; D016166:Free Radical Scavengers / Q000494:pharmacology; D041981:Gastrointestinal Tract / Q000187:drug effects*; D006162:Guanylate Cyclase / Q000378:metabolism; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology*; D012996:Solutions; D013482:Superoxide Dismutase / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D016166:Free Radical Scavengers; D012996:Solutions; D014665:Vasodilator Agents; D009599:Nitroprusside; D001120:Arginine; D013482:Superoxide Dismutase; D006162:Guanylate Cyclase