title: Excess l-arginine restores endothelium-dependent relaxation impaired by monocrotaline pyrrole.
abstract: The pyrrolizidine alkaloid plant toxin monocrotaline pyrrole (MCTP) causes pulmonary hypertension in experimental animals. The present study aimed to examine the effects of MCTP on the endothelium-dependent relaxation. We constructed an in vitro disease model of pulmonary hypertension by overlaying MCTP-treated bovine pulmonary artery endothelial cells (CPAEs) onto pulmonary artery smooth muscle cell-embedded collagen gel lattice. Acetylcholine (Ach) induced a relaxation of the control CPAEs-overlaid gels that were pre-contracted with noradrenaline, and the relaxation was inhibited by L-NAME, an inhibitor of NO synthase (NOS). In contrast, when MCTP-treated CPAEs were overlaid, the pre-contracted gels did not show a relaxation in response to Ach in the presence of 0.5 mM l-arginine. Expression of endothelial NOS protein, Ach-induced Ca2+ transients and cellular uptake of l-[3H]arginine were significantly smaller in MCTP-treated CPAEs than in control cells, indicating that these changes were responsible for the impaired NO production in MCTP-treated CPAEs. Since cellular uptake of l-[3H]arginine linearly increased according to its extracellular concentration, we hypothesized that the excess concentration of extracellular l-arginine might restore NO production in MCTP-treated CPAEs. As expected, in the presence of 10 mM l-arginine, Ach showed a relaxation of the MCTP-treated CPAEs-overlaid gels. These results indicate that the impaired NO production in damaged endothelial cells can be reversed by supplying excess l-arginine.
authors.affiliation: Department of Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-82, Japan.
authors.forename: Wei
authors.initials: W
authors.lastname: Cheng
authors.forename: Masahiro
authors.initials: M
authors.lastname: Oike
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hirakawa
authors.forename: Keizo
authors.initials: K
authors.lastname: Ohnaka
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Koyama
authors.forename: Yushi
authors.initials: Y
authors.lastname: Ito
mesh_terms: D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002452:Cell Count; D048429:Cell Size; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016686:Monocrotaline / Q000031:analogs & derivatives* / Q000633:toxicity; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D052250:Nitric Oxide Synthase Type III
chemical_list: D004791:Enzyme Inhibitors; C014114:monocrotaline pyrrole; D016686:Monocrotaline; D001120:Arginine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester