title: Endothelium-dependent vasorelaxation in inhibited by in vivo depletion of vascular thiol levels: role of endothelial nitric oxide synthase.
abstract: Thiols like glutathione may serve as reducing cofactors in the production of nitric oxide (NO) and protect NO from inactivation by radical oxygen species. Depletion of thiol compounds reduces NO-mediated vascular effects in vitro and in vivo. The mechanisms underlying these actions are not clear, but may involve decreased synthesis of NO and/or increased degradation of NO. This study investigates the effect of glutathione depletion on the response to NO-mediated vasodilation induced by acetylcholine (Ach, 10 micrograms/kg), endothelial NO synthase (eNOS) activity and potential markers of vascular superoxide anion (O2.-) production in conscious chronically catheterized rats. Thiol depletion induced by buthionine sulfoximine (BSO, 1 g i.p. within 24 h) decreased the hypotensive effect of Ach by 30% (MAP reduction before BSO 27 +/- 3 mmHg, 19 +/- 3 mmHg after BSO, (mean +/- SEM), p < .05, n = 8). The impaired effect of Ach was associated with a significant reduction in eNOS activity (control: 7.7 +/- 0.8, BSO: 3.9 +/- 0.4 pmol/min/mg protein (p < .05), n = 6). In contrast, neither NADH/NADPH driven membrane-associated oxidases nor lucigenin reductase activity were significantly (p < .05) affected by BSO (BSO: 4415 +/- 123, control: 4105 +/- 455 counts/mg; n = 6) in rat aorta. It is concluded that in vivo thiol depletion results in endothelial dysfunction and a reduced receptor-mediated vascular relaxation. This effect is caused by reduced endothelial NO formation.
authors.affiliation: Medical Department B, Division of Cardiology, Institute of Biochemistry, Department of Clinical Pharmacology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark. jb137@hotmail.com
authors.forename: J B
authors.initials: JB
authors.lastname: Laursen
authors.forename: S
authors.initials: S
authors.lastname: Boesgaard
authors.forename: S
authors.initials: S
authors.lastname: Trautner
authors.forename: I
authors.initials: I
authors.lastname: Rubin
authors.forename: H E
authors.initials: HE
authors.lastname: Poulsen
authors.forename: J
authors.initials: J
authors.lastname: Aldershvile
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D001011:Aorta / Q000187:drug effects; D001794:Blood Pressure; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000201:enzymology*; D005260:Female; D005978:Glutathione / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species; D014664:Vasodilation / Q000502:physiology*
chemical_list: D000963:Antimetabolites; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D019328:Buthionine Sulfoximine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D005978:Glutathione; D000109:Acetylcholine