NITRIC OXIDE: THE SAVIOUR.

Nitric oxide (NO) is one of the nitrogen oxides and is synthesized within cells by an enzyme NO synthase. It  was formerly known as endothelium-derived relaxing factor (EDRF).  Being one of the fundamental mediators in physiological processes, this enzyme catalyses the oxidation of L-arginine to L-citrulline, producing NO, which diffuses into vascular smooth muscle, activating guanylate cyclase  which in turn converts guanosine triphosphate into cyclic guanosine monophosphate (cGMP),causing vascular relaxation.
                                 Nitric oxide synthetase is present in two forms a)The constitutive form (eNOS), which is present in vascular, neuronal, cardiac tissue, skeletal muscle and platelets, producing small quantities of NO continuously. Here NOS is Ca2+/calmodulin dependant and is stimulated by cGMP.and b)the inducible form (iNOS),present in endo thelium, myocytes, macrophages and neutrophils, which produces relatively large quatities of NO after exposure to endotoxins in sepsis.

Biological effects of Nitric oxide ;
• Vascular endothelium: producing vascular relaxation.
• Platelets: involved in aggregation and adhesion of platelets
• Brain tissue: acts as a neurotransmitter.
• Macrophages: involved in the response to infection.