Nitric oxide
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Transcript of Nitric oxide
M.Prasad NaiduMSc Medical Biochemistry,
Ph.D.Research Scholar
NONitric oxide possess more biological potential functions.Nitric oxide an uncharged molecule having an unpaired election.
It is highly free radical NOLipid soluble freely diffuse across half life is very short about 0.1 second.
SynthesisNO is synthesized from argenine by nitric oxide synthase (NOS).it is a dimeric proteincontain Heme
FADFMNTetrahydrobiopterineCalmodulin
The enzyme is dioxygenase
It utilizes molecular oxygenOne oxygen atom form NOOther in corporated into citrulline
NO reacts with oxygen Nitrite Excreted in the urine
Reacts with Haemoglobin NO is Nitrates
On exposed to superoxide (O2-) nitric acid No &
peroxynitrite (OONO) Causes lipid peroxidation ; cell injury and cell death.
Iso enzymes of Nitric oxide synthase.Three Isoforms from 3 different genes
Neuronal NOSNOSI or nNOS seen in central and peripheral neurons.Gene is on chromosome 12
Nitrogenic neurons are seen especially in cerebellum and gastrointestinal tract,Cytoplasmic enzyme activated by calcium.Macrophage NOS , NOS2 or inducible NOSMacrophage NOS is mostly present in macrophages & neutrophils.To a lesser extent present in hepatocytes .it is induced by cytokines & during inflammatory reactions
it is a cytoplasmic enzyme but not activated by calcium .
Gene is on chromosome 17 .NOS 3 or endothelial NOS Gene is on chromosome 7Activated by calcium It is seen in endothelial cells , platelets
endocardium & myocardium .
Localized in plasma membrane .Activated by calcium .Functions of Nitric oxide :1)On blood vessels potent vasodilator
Decreased concentration of nitric oxide leads to hypertention .NOS is seen only in arterioles not in venules.
2)Platelets : inhibits adhesion of platelets .3)GIT : NO is nonadrenergic non cholinergic
neurotransmitter in GIT & urinarytract .
Reduces gastric motility & relaxes sphincters .
Infantile hypertrophic pyloric stenosis & Hirschsprung’s disease
Nitric oxide is considered as a memory molecule .
NO stimulates release of hormones like CRH , GNRH , LHRH .
In macrophage NO production is induced by interleukin & tumor necrosis factor .
NO in diseases & treatment1) Angina pectoris2) Pulmonary hypertention 3) Impotence 4) ShockAntagonists of NO : N- Mono methyl arginine
( NMMA ), competitively inhibits NOS .Asymmetric dimethyl arginine ( ADMA ) arginine
analogue acts as NOS inhibitor .Increased in hyperhomocysteinemia &
preeclampsia – increased B.P