Excess l-arginine restores endothelium-dependent relaxation impaired by monocrotaline pyrrole.
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.
Cheng
Wei
W
Department of Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-82, Japan.
Oike
Masahiro
M
Hirakawa
Masakazu
M
Ohnaka
Keizo
K
Koyama
Tetsuya
T
Ito
Yushi
Y
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
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