title: Endothelial nitric oxide synthase is a site of superoxide synthesis in endothelial cells treated with glyceryl trinitrate.
abstract: Tolerance to glyceryl trinitrate (GTN) involves superoxide (O(2)(*-)) production by endothelial cells. Nitric oxide synthase (NOS) produces O(2)(*-) when L-arginine (L-arg) is limited. The purpose of this study was to test the hypothesis that GTN stimulates NOS to increase O(2)(*-) synthesis in endothelial cells when L-arg is limited. Production of O(2)(*-) by bovine aortic endothelial cells (BAEC, passages 3 - 5) was determined by spectrophotometrically measuring superoxide dismutase-inhibited reduction of ferricytochrome C to ferrocytochrome C. Cells were incubated in buffer without L-arg. O(2)(*-) production was measured using BAEC either untreated or treated with L-NAME or L-arg alone or following treatment with GTN (10(-9) to 10(-6) M) for 30 min or DPTA NONOate (10(-7) and 10(-6) M) alone or with GTN or DPTA NONOate after pretreatment with nitro-L-arginine methyl ester (L-NAME), L-arg or their inactive enantiomers, D-NAME or D-arg (all 5 x 10(-4) M) (n=6 - 7/group). L-NAME alone produced a 69% reduction in O(2)(*-) levels. Treatment with L-arg alone had no effect. Cells treated with GTN alone exhibited an increase in O(2)(*-). This effect was prevented by pretreatment with either L-NAME or L-arg, and was unaffected by D-NAME or D-arg. We observed a dose-response relationship in O(2)(*-) production to GTN over a range of 10(-9) to 10(-7) M. The NO donor, DPTA-NONOate, unlike GTN, did not have a significant effect on O(2)(*-) production. In conclusion, endothelial NOS is a site of O(2)(*-) synthesis in endothelial cells activated by GTN.
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Georgia, Laney-Walker Boulevard, Augusta, Georgia, GA 30912, USA.
authors.forename: W H
authors.initials: WH
authors.lastname: Kaesemeyer
authors.forename: A A
authors.initials: AA
authors.lastname: Ogonowski
authors.forename: L
authors.initials: L
authors.lastname: Jin
authors.forename: R B
authors.initials: RB
authors.lastname: Caldwell
authors.forename: R W
authors.initials: RW
authors.lastname: Caldwell
mesh_terms: D000818:Animals; D001120:Arginine / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D005996:Nitroglycerin / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism*
chemical_list: D013481:Superoxides; D001120:Arginine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D005996:Nitroglycerin; D019331:NG-Nitroarginine Methyl Ester