Nitric oxide alteration in the cardiovascular function by exercise training Altera o do óxido nítrico na fun o cardiovascular pelo treinamento físico

Among the mechanisms of arterial pressure control, the humoral one carried out by the nitric oxide (NO) has aroused great scientific interest. The cardiovascular effects observed after the physical training are associated to an increase in the vascular structure, resting bradycardia and a post effort hypotension effect. The NO that is synthesized in endothelial cells from the L-arginine amino acid with the nitric oxide synthase (NOS) action is considered a powerful vaso-dilator. The NO has three enzymatic isoforms: the nNOS enzyme is present in the nervous cells, and the eNOS in the endothelial cells, both calciumdependent. On the other hand, the iNOS which is activated by immunological stimuli, is calciumindependent. In the central nervous system (CNS), the NO exerts an important role in the blood pressure control through sympathetic nervous system, inhibiting its activity and decreasing the vascular tonus. Moreover, the NO exerts an influence on the rostral ventrolateral medulla (RVLM), which is important in the modulation of the cardiovascular function. Studies that relate physical training and NO, noticed a significant increase in vasodilation after physical training in special population such as: hypertensives, obese, diabetic and cardiopath people, when compared with healthy individuals. In this sense, there seems to be a modulation of the physical training on the NO participation in the PA control, not only in the peripherical but also in the central level. New studies are still necessary to better elucidate this phenomenon. Dentre os mecanismos de controle da press o arterial, o controle humoral realizado pelo óxido nítrico (NO) tem despertado grande interesse científico. Os efeitos cardiovasculares observados após o treinamento físico est o associados ao aumento da estrutura vascular, bradicardia de repouso e um efeito hipotensor após esfor o. O NO, sintetizado em células endoteliais a partir do aminoácido Larginina com a a o da enzima óxido nítrico sintase (NOS), é considerado um potente vasodilatador. O NO possui três isoformas enzimáticas: a enzima nNOS atua nas células nervosas e a eNOS em células endoteliais (ambas cálcio dependentes) e a iNOS, é ativada por estímulos imunológicos e independente do íon cálcio. No sistema nervoso central (SNC), o NO possui importante papel no controle da press o sanguínea via sistema nervoso simpático, pois inibe sua atividade e diminui seu t nus sobre os vasos. Além disso, o NO exerce influência na regi o ventrolateral rostral medular (RVLM), importante na modula o da fun o cardiovascular. Estudos que r