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Glomerular and vascular tissues do not down-regulate nitric oxide synthesis during protracted endotoxemia
D del Castillo1, A Agarwal, E A Jaimes
1Veterans Affairs Medical Center, Minneapolis, Minnesota, USA.
Kidney International
|August 1, 1997
Summary
Endotoxin tolerance down-regulates nitric oxide (NO) production in rats, particularly in the liver, spleen, and macrophages, while vascular tissues maintain elevated NO levels. This suggests a specific down-regulation mechanism in certain organs during prolonged endotoxin exposure.
Area of Science:
- Immunology
- Physiology
- Pharmacology
Background:
- Cytokine down-regulation is key to tolerance against bacterial products.
- Nitric oxide (NO) mediates many effects of endotoxin and cytokines.
- Understanding the L-arginine:NO pathway in endotoxin tolerance is crucial.
Purpose of the Study:
- To investigate the in vivo L-arginine:NO pathway during endotoxin tolerance.
- To determine how prolonged exposure to lipopolysaccharide (LPS) affects NO production in different rat tissues.
Main Methods:
- Rats received daily sublethal injections of E. coli lipopolysaccharide (LPS) for five days.
- Measured blood and urinary levels of NO2-/NO3- (stable NO metabolites).
- Assessed NO production in isolated glomeruli, aortae, peritoneal macrophages, liver, and spleen, both in vivo and in vitro.
Main Results:
- Blood NO2-/NO3- levels initially increased then returned to baseline; urinary levels remained elevated.
- Glomeruli and aortae showed sustained NO production, increasing further with in vitro LPS challenge.
- Macrophages, liver, and spleen exhibited initial NO increase followed by significant decrease, unresponsive to in vitro LPS.
Conclusions:
- Protracted LPS exposure leads to down-regulation of in vivo NO synthesis.
- This down-regulation is specific to organs like the liver, spleen, and macrophages.
- NO production differs qualitatively and quantitatively between vascular tissues and other organs during endotoxin tolerance.