[Nitric oxide. Basic research and possible clinical use].

Abstract

The journal Science considered nitric oxide (NO) the molecule of the year 1992. This small, instable, potentially toxic gas freely crosses cell membranes. NO is produced from L-arginine by NO-synthase. The various physiological and pathological effects of NO can be explained by its reactivity and different routes of formation and metabolism. In mammals, at least three isoenzymes of NO-synthase (neuronal, endothelial and inducible forms) are known. NO exerts different effects in acidic, neutral and basic pH conditions, it is cell-protective when produced is small quantities whereas it is toxic when exceeds millimolar concentrations. Both the overproduction and suppression of NO release may have harmful effects. As a neurotransmitter, it plays important role in cell-signaling, in the erection of penis and also in the learning process. When produced by endothelial cells, it is a potent vasodilatator, and phagocytes use NO to kill microorganisms. NO also may play pathological role in chronic inflammations, immune processes and tumour generation. Based an our current knowledge, NO can be used in the therapy of pulmonary hypertension, cerebral ischemia and relaxation disturbances of smooth muscle sphincters, and the blockade of NO synthase activity may help in the management of septic shock, hypotension and inflammations.