[The cardiovascular significance of nitric oxide]

Nitric oxide (NO) synthesized from L-arginine is a ubiquitous intercellular chemical messenger involved in signal transduction in diverse mammalian cells. The isolation of molecular clones for NO synthases has permitted the characterization of several distinct enzyme isoforms. NO synthesized in vascular endothelial cells plays an important role in the control of vascular tonus and platelet aggregation, through the activation of guanylate-cyclase activity in target tissues mediated by NO. Nitric oxide which is produced by cytokine activated mononuclear cells plays an important role in inflammation and immunity as a cytotoxic effector molecule and as a transducer molecule in immune cells and in oxidative stress as a potential source of intracellular free radicals. An increase in reactive oxygen species can produce damage to lipids, proteins and DNA and induce necrosis or apoptosis. The implication of NO in different pathological processes, such as atherosclerosis, diabetes, ischaemia and reperfusion, or during inflammatory processes and the generation of free radicals contributing to the endothelial injury associated to these processes.