title: Human heart mitochondria do not produce physiologically relevant quantities of nitric oxide.
abstract: Previous studies raised the possibility that nitric oxide synthase is present in heart mitochondria (mtNOS) and the existence of such an enzyme became generally accepted. However, original experimental evidence is rather scarce and positive identification of the enzyme is lacking. We aimed to detect an NOS protein in human and mouse heart mitochondria and to measure the level of NO released from the organelles. Western blotting with 7 different anti-NOS antibodies failed to detect a NOS-like protein in mitochondria. Immunoprecipitation or substrate-affinity purification of the samples concentrated NOS in control preparations but not in mitochondria. Release of NO from live respiring human mitochondria was below 2 ppb after 45 min of incubation. In a bioassay system, mitochondrial suspension failed to cause vasodilation of human mammary artery segments. These results indicate that mitochondria do not produce physiologically relevant quantities of NO in the heart and are unlikely to have any physiological importance as NO donors, nor do they contain a recognizable mtNOS enzyme.
authors.affiliation: Department of Human Physiology and Clinical Experimental Research, Semmelweis University, Budapest, Hungary.
authors.forename: Attila
authors.initials: A
authors.lastname: Csordás
authors.forename: Eszter
authors.initials: E
authors.lastname: Pankotai
authors.forename: James A
authors.initials: JA
authors.lastname: Snipes
authors.forename: Attila
authors.initials: A
authors.lastname: Cselenyák
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Sárszegi
authors.forename: Attila
authors.initials: A
authors.lastname: Cziráki
authors.forename: Balázs
authors.initials: B
authors.lastname: Gaszner
authors.forename: Lajos
authors.initials: L
authors.lastname: Papp
authors.forename: Rita
authors.initials: R
authors.lastname: Benko
authors.forename: Levente
authors.initials: L
authors.lastname: Kiss
authors.forename: Endre
authors.initials: E
authors.lastname: Kovács
authors.forename: Márk
authors.initials: M
authors.lastname: Kollai
authors.forename: Csaba
authors.initials: C
authors.lastname: Szabó
authors.forename: David W
authors.initials: DW
authors.lastname: Busija
authors.forename: Zsombor
authors.initials: Z
authors.lastname: Lacza
mesh_terms: D000818:Animals; D015153:Blotting, Western; D006801:Humans; D051379:Mice; D008929:Mitochondria, Heart / Q000201:enzymology*; D009569:Nitric Oxide / Q000032:analysis / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000378:metabolism*
chemical_list: D009569:Nitric Oxide; D019001:Nitric Oxide Synthase