title: Effects of L-arginine on spontaneous contraction of the rat portal vein.
abstract: The effects of L-arginine on spontaneous contraction of endothelium-denuded longitudinal preparations of the rat portal vein were studied. L-arginine increased the frequency of spontaneous contraction concentration-dependently between 10 microM and 1 mM. Changes in contraction amplitude and duration were not remarkable. D-arginine had a negligible effect on spontaneous contraction. N(omega)-nitro-L-arginine (1 mM) did not affect spontaneous contraction or the response to L-arginine. Addition of N(G)-monomethyl-L-arginine (1 mM), l-lysine (1 mM) or N-ethymaleimide (0.1 mM) increased the frequency of spontaneous contractions and inhibited the effect of L-arginine. Glibenclamide (10 microM) did not affect spontaneous contraction or the response to L-arginine. Spontaneous increase in concentration of intracellular Ca2+, estimated as the ratio of Fura-PE3 fluorescence occurred synchronously with spontaneous contraction. Spontaneous increase in concentration of intracellular Ca2+ occurred more frequently in the presence of L-arginine (1 mM). L-arginine (1 mM) also increased the number of action potential bursts/min in the longitudinal smooth muscle layer. L-arginine (1 mM) also depolarized cell membranes. This study indicates that L-arginine increases the frequency of spontaneous contraction of longitudinal muscle in the rat portal vein by membrane depolarization through mechanisms that do not involve nitric oxide or the inhibition of ATP-sensitive K+ channels.
authors.affiliation: Department of Clinical Pharmacology, Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, 1757 Kanazawa, Ishikari-Tobetsu, Hokkaido 061-0293, Japan. shimamu@hoku-iryo-u.ac.jp
authors.forename: Keiichi
authors.initials: K
authors.lastname: Shimamura
authors.forename: Ming
authors.initials: M
authors.lastname: Zhou
authors.forename: Miyuki
authors.initials: M
authors.lastname: Toba
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kimura
authors.forename: Takashiro
authors.initials: T
authors.lastname: Higuchi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kawaguchi
authors.forename: Fumiko
authors.initials: F
authors.lastname: Sekiguchi
authors.forename: Satoru
authors.initials: S
authors.lastname: Sunano
mesh_terms: D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D011169:Portal Vein / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D014662:Vasoconstrictor Agents; D001120:Arginine; D002118:Calcium