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Nitric oxide synthase activity in rat cardiac mitochondria
Barbara Zanella1, Emanuele Giordano, Claudio Muscari
1Department of Biochemistry, "G. Moruzzi" University of Bologna, Via Irnerio 48, 40126, Bologna, Italy. bzanella@biocfarm.unibo.it
Basic Research in Cardiology
|April 17, 2004
Summary
Mitochondria in rat hearts contain both constitutive and inducible nitric oxide synthase (NOS) enzymes. This dual mitochondrial NOS system may regulate cardiac oxygen consumption in various conditions.
Area of Science:
- Biochemistry
- Cardiology
- Molecular Biology
Background:
- Mitochondrial localization of nitric oxide synthase (NOS) has been reported in various tissues.
- Conflicting data exist regarding mitochondrial NOS (mtNOS) immunoreactivity and enzymatic activity.
Purpose of the Study:
- To investigate the presence and activity of NOS isoforms within purified rat heart mitochondria.
- To elucidate the role of mtNOS in cardiac function.
Main Methods:
- Mitochondria were isolated from rat hearts.
- NOS immunoreactivity and activity were analyzed.
- Inhibition studies were performed using L-NMMA and GW274150.
- Calcium (Ca2+) and calmodulin (CaM) interference was assessed.
Main Results:
- Rat heart mitochondria exhibited both constitutive (endothelial) and inducible NOS immunoreactivity.
- A basal NOS activity was detected and partially inhibited by L-NMMA.
- Specific inhibition of NOS2 (using GW274150) and Ca2+/CaM withdrawal significantly reduced NOS activity.
- A dual mtNOS system was identified.
Conclusions:
- Rat heart mitochondria possess a dual NOS system comprising both constitutive and inducible isoforms.
- This mtNOS machinery is implicated in modulating cardiac oxygen consumption under physiological and pathological conditions.