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Kidney mitochondrial nitric oxide synthase
Alberto Boveris1, Laura B Valdez, Silvia Alvarez
1Laboratory of Free Radical Biology, School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina. aboveris@ffyb.uba.ar
Abstract:
Nitric oxide synthase activity was recognized in rat renal cortex mitochondria (mtNOS) with nitric oxide (NO) production rates of 0.14-0.78 nmol/min/mg of protein. Rat pretreatment with enalapril (30 mg/kg/day i.p., up to 15 days) increased NO production in kidney, liver, and heart mitochondria. In kidney, mtNOS activity and mtNOS protein, measured by western blot densitometry, were 5 and 2.3 times increased, respectively. Electron paramagnetic resonance analysis with the probe N-methyl-D-glucamine dithiocarbamate/FeSO(4) detected NO production in mitochondria isolated from enalapril-treated rats, but not in control untreated animals. Polyclonal antibodies anti-iNOS and anti-nNOS detected kidney mtNOS in western blots and inhibited mtNOS biochemical activity. The enzymatic activity of kidney mtNOS generates intramitochondrial NO concentrations that regulate mitochondrial functions: state 3 respiration was decreased by 12-28%, and state 4 hydrogen peroxide production was increased 12-35%.
Insights
Enalapril treatment significantly boosted nitric oxide synthase (NOS) activity in rat mitochondria, increasing nitric oxide (NO) production. This enhanced mitochondrial NO impacts cellular respiration and hydrogen peroxide levels.
Area of Science:
- Mitochondrial biochemistry
- Pharmacology
- Physiology
Background:
- Mitochondrial nitric oxide synthase (mtNOS) plays a role in cellular function.
- The effects of ACE inhibitors like enalapril on mtNOS are not fully understood.
Purpose of the Study:
- To investigate the impact of enalapril on mtNOS activity and nitric oxide (NO) production in rat mitochondria.
- To determine how changes in mtNOS activity affect mitochondrial function.
Main Methods:
- Measurement of NO production in isolated kidney, liver, and heart mitochondria.
- Western blot analysis for mtNOS protein levels.
- Electron paramagnetic resonance (EPR) spectroscopy to detect NO.
- Assessment of mitochondrial respiration and hydrogen peroxide production.
Main Results:
- Enalapril treatment increased NO production in kidney, liver, and heart mitochondria.
- Kidney mtNOS activity and protein levels were significantly elevated (5-fold and 2.3-fold, respectively).
- Enalapril-induced mtNOS activity decreased state 3 respiration and increased state 4 hydrogen peroxide production.
Conclusions:
- Enalapril enhances mtNOS activity and NO production in rat mitochondria.
- Intramitochondrial NO generated by mtNOS modulates mitochondrial respiration and oxidative stress.
- These findings suggest a novel mechanism for enalapril's action involving mitochondrial function.