ESPÉCIES REATIVAS DE OXIGÊNIO NO CONTROLE NEUROVEGETATIVO DA PRESSÃO ARTERIAL

The control of the blood pressure depends on the activity of select groups of neurons present in the central nervous system. Evidence has demonstrated that the redox state (a balance between oxidizing and reducing species) is involved in the control of neuronal activity, which suggests that the redox state can influence the neuronal transmission within the central nervous system acting on the neuronal modulation of biological functions. For instance, the glutamatergic transmission may be widely affected by reactive oxygen species, oxidizing agents that have been extensively investigated due to their involvement in physiological and pathological processes. In the present article, we discuss the main experimental finds that support the hypothesis that reactive oxygen species have important role in physiological (and pathological) modulation of the cardiovascular function through alterations in the sympathetic and parasympathetic system. Therefore, reactive oxygen species can actively participate in the development of cardiovascular diseases like hypertension when the balance in the redox state is disrupted.Existem evidências de que a atividade neuronal pode ser modulada pelo estado redox (balanço entre espécies químicas oxidantes e redutoras) das células, influenciando, assim, as diferentes funções biológicas que são controladas pelo sistema nervoso. Essa modulação pode ocorrer por meio de diferentes mecanismos e um deles é a modulação da transmissão sináptica no sistema nervoso central (SNC). As descargas autonômicas que são controladas por mecanismos localizados em diferentes áreas do SNC são fundamentais para o controle da pressão arterial. Um importante neurotransmissor que participa dos mecanismos centrais de controle cardiovascular é o glutamato e a transmissão glutamatérgica pode ser extensamente afetada por espécies reativas de oxigênio, oxidantes que parecem ter um importante papel em processos fisiológicos e patológicos. No presente artigo são apresentados os principais achados experimentais que suportam a hipótese de que as espécies reativas de oxigênio podem modular as funções cardiovasculares por produzir alterações nos mecanismos centrais de controle dos sistemas simpático e parassimpático. Logo, desequilíbrios na sinalização mediada por espécies reativas de oxigênios podem contribuir para o desenvolvimento de doenças cardiovasculares como a hipertensão

Role of the Renin Angiotensin System in Blood Pressure Allostasis-induced by Severe Food Restriction in Female Fischer rats

Severe food restriction (FR) is associated with blood pressure (BP) and cardiovascular dysfunction. The renin-angiotensin system (RAS) regulates BP and its dysregulation contributes to impaired cardiovascular function. Female Fischer rats were maintained on a control (CT) or severe FR (40% of CT) diet for 14 days. In response to severe FR, BP allostasis was achieved by up-regulating circulating Ang-[1-8] by 1.3-fold through increased angiotensin converting enzyme (ACE) activity and by increasing the expression of AT1Rs 1.7-fold in mesenteric vessels. Activation of the RAS countered the depressor effect of the severe plasma volume reduction (≥30%). The RAS, however, still underperformed as evidenced by reduced pressor responses to Ang-[1-8] even though AT1Rs were still responsive to the depressor effects of an AT1R antagonist. The aldosterone (ALDO) response was also inadequate as no changes in plasma ALDO were observed after the large fall in plasma volume. These findings have implications for individuals who have experienced a period(s) of severe FR (e.g., anorexia nervosa, dieters, natural disasters) and suggests increased activity of the RAS in order to achieve allostasis contributes to the cardiovascular dysfunction associated with inadequate food intake

Elimination of turbidity interference in serum iron colorimetric assay by enzymatic proteolysis

We describe a modification in the commercial colorimetric method for the determination of serum iron by using Ferrozine® . The modification was proposed because during the conventional procedure, turbidity observed when the serum of animals submitted to surgery was used interfered with the assay. We added to the original method, a previous treatment of the serum with proteolytic enzymes. This modification was also tested using plasma samples, although this was not recommended when the original method was used. The results demonstrated that: a) the treatment with a mixture of trypsin and chymotrypsin was effective in order to eliminate turbidity; b) there was no difference between the standard curves obtained by the conventional and the modified method for control assays; c) the absorbencies of the samples of serum and plasma submitted to proteolysis, estimated by the addition of different concentrations of iron, were directly proportional to iron concentrations; d) the pre-treatment with enzymes allowed the utilization of plasma; e) the pre-treatment with guanidine. HCl was not effective

Espécies reativas de oxigênio no controle neurovegetativo da pressão arterial

The control of the blood pressure depends on the activity of select groups of neurons present in the central nervous system. Evidence has demonstrated that the redox state (a balance between oxidizing and reducing species) is involved in the control of neuronal activity, which suggests that the redox state can influence the neuronal transmission within the central nervous system acting on the neuronal modulation of biological functions. For instance, the glutamatergic transmission may be widely affected by reactive oxygen species, oxidizing agents that have been extensively investigated due to their involvement in physiological and pathological processes. In the present article, we discuss the main experimental finds that support the hypothesis that reactive oxygen species have important role in physiological (and pathological) modulation of the cardiovascular function through alterations in the sympathetic and parasympathetic system. Therefore, reactive oxygen species can actively participate in the development of cardiovascular diseases like hypertension when the balance in the redox state is disrupted

Elimination of turbidity interference in serum iron colorimetric assay by enzymatic proteolysis

We describe a modification in the commercial colorimetric method for the determination of serum iron by using Ferrozine® . The modification was proposed because during the conventional procedure, turbidity observed when the serum of animals submitted to surgery was used interfered with the assay. We added to the original method, a previous treatment of the serum with proteolytic enzymes. This modification was also tested using plasma samples, although this was not recommended when the original method was used. The results demonstrated that: a) the treatment with a mixture of trypsin and chymotrypsin was effective in order to eliminate turbidity; b) there was no difference between the standard curves obtained by the conventional and the modified method for control assays; c) the absorbencies of the samples of serum and plasma submitted to proteolysis, estimated by the addition of different concentrations of iron, were directly proportional to iron concentrations; d) the pre-treatment with enzymes allowed the utilization of plasma; e) the pre-treatment with guanidine. HCl was not effective

Oxidative stress causes hypertension and activation of nuclear factor-κB after high-fructose and salt treatments

International audienceThere is evidence that diets rich in salt or simple sugars as fructose are associated with abnormalities in blood pressure regulation. However, the mechanisms underlying pathogenesis of salt- and fructose-induced kidney damage and/or consequent hypertension yet remain largely unexplored. Here, we tested the role of oxidative state as an essential factor along with high salt and fructose treatment in causing hypertension. Fischer male rats were supplemented with a high-fructose diet (20% in water) for 20 weeks and maintained on high-salt diet (8%) associate in the last 10 weeks. Fructose-fed rats exhibited a salt-dependent hypertension accompanied by decrease in renal superoxide dismutase activity, which is the first footprint of antioxidant inactivation by reactive oxygen species (ROS). Metabolic changes and the hypertensive effect of the combined fructose-salt diet (20 weeks) were markedly reversed by a superoxide scavenger, Tempol (10 mg/kg, gavage); moreover, Tempol (50 mM) potentially reduced ROS production and abolished nuclear factor-kappa B (NF-κB) activation in human embryonic kidney HEK293 cells incubated with L-fructose (30 mM) and NaCl (500 mosmol/kg added). Taken together, our data suggested a possible role of oxygen radicals and ROS-induced activation of NF-κB in the fructose- and salt-induced hypertension associated with the progression of the renal disease

Dietary models for inducing hypercholesterolemia in rats

The present work aimed at finding a dietetical model capable of promoting the highest hypercholesterolemia without affecting the development of the rats. Sixty female Fisher rats were divided into five groups. The first one was fed a control diet; the remaining four were fed hypercholesterolemic diets with cholesterol and different contents of soybean oil, starch, casein, micronutrients and fiber and, consequently, different caloric values. After eight weeks animals were evaluated in relation to growth, fecal excretion, liver weight and fat, cholesterol and its fractions, serum biochemical parameters and sistolic pressure and compared with controls. The best result was obtained with the diet containing 25 % soybean oil, 1.0 % cholesterol, 13 % fiber and 4,538.4 Kcal/Kg, since it promoted an increase in LDL-cholesterol, a decrease in the HDL fraction and affected less the hepatic function of the animals.<br>Modelos animais têm sido usados para investigar a relação entre desordens no metabolismo do colesterol e a aterogênese. A estratégia utilizada a fim de induzir hipercolesterolemia (dietas com alto teor de gordura e com colesterol adicionado) leva à redução de sua ingestão pelos animais, o que induz desnutrição. O presente trabalho objetivou encontrar um modelo dietético capaz de promover a maior hipercolesterolemia, sem afetar o desenvolvimento dos animais. Sessenta ratas Fisher foram divididas em cinco grupos. O primeiro foi alimentado com uma dieta controle; os quatros restantes receberam dietas hipercolesterolêmicas, com colesterol e diferentes teores de óleo de soja, amido, caseína, micronutrientes e fibra e, conseqüentemente, diferentes valores calóricos. Após oito semanas os animais foram avaliados em relação ao crescimento, excreção fecal, peso e teor de gordura do fígado, colesterol e suas frações, parâmetros bioquímicos séricos e pressão sistólica. Os melhores resultados foram obtidos com a dieta contendo 25% de óleo de soja, 1% de colesterol, 13% de fibra e 4.538,4 Kcal/Kg, uma vez que promoveu aumento no LDL-colesterol, decréscimo no HDL-colesterol e afetou menos a função hepática dos animais