Nitric oxide: A review for veterinary surgeons

Nitric oxide (NO) is an endogenous gas that serves as a biologic messenger in many physiologic processes including neurotransmission, blood-pressure c ontrol, the immune system's ability to kill tumor cells, and wound healing, NO is produced after oxidation of L-arginine by a family of nitric oxide s ynthase (NOS) enzymes. Two of the NOS enzymes are present continuously and are thereby termed constitutive NOS. One of the enzymes, inducible NOS, is not typically expressed in resting cells and is induced by various substanc es including endotoxin, some cytokines, and microbial products. Thus, NO of ten has paradoxical activities. When NO is over- or underproduced, it can r esult in potentiation of disease states with disastrous results. This revie w discusses the biochemistry of NO, its functions in normal and disease sta tes, and therapy for modulating NO production in disease states. (C) Copyri ght 2001 by The American College of Veterinary Surgeons.