title: Lack of critical involvement of endothelial nitric oxide synthase in vascular nitrate tolerance in mice.
abstract: We examined the direct involvement of endothelial nitric oxide (eNOS) in nitrate tolerance using eNOS knockout (eNOS (-/-)) and wild-type (eNOS (+/+)) mice. Animals were treated with either nitroglycerin (NTG, 20 mg kg(-1)s.c. 3 x daily for 3 days) or vehicle (5% dextrose, D5W), and nitrate tolerance was assessed ex vivo in isolated aorta by vascular relaxation studies and cyclic GMP accumulation. Western blot was performed to determine NOS expression after NTG treatment. In both the eNOS (-/-) and (+/+) mice, the EC(50) from NTG concentration-response curve was increased by approximately 3 fold, and vascular cyclic GMP accumulation was similarly decreased after NTG pretreatment. Vascular tolerance did not lead to changes in eNOS protein expression in eNOS (+/+) mice. These results indicate that vascular nitrate tolerance was similarly induced in eNOS (-/-) and (+/+) mice, suggesting that eNOS may not be critically involved in nitrate tolerance development in mice.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, SUNY, Buffalo, NY 14260-1200, USA.
authors.forename: Ellen Q
authors.initials: EQ
authors.lastname: Wang
authors.forename: Woo-In
authors.initials: WI
authors.lastname: Lee
authors.forename: Ho-Leung
authors.initials: HL
authors.lastname: Fung
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000201:enzymology; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009566:Nitrates / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D005996:Nitroglycerin / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects* / Q000235:genetics; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D009566:Nitrates; D014665:Vasodilator Agents; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D005996:Nitroglycerin; D006152:Cyclic GMP