Shock hemorrágico: óxido nítrico en ratas anestesiadas y no anestesiadas / Hemorrhagic Shock: Nitric Oxide in Anesthetized and Non Anesthetized Rats

Antecedentes En un trabajo previo mostramos que el estado hipovolémico inducido por una pérdida aguda de sangre se acompaña de una activación dinámica, heterogénea y dependiente del tiempo de la óxido nítrico sintetasa (NOS) cardíaca. Este sistema estaría involucrado en las alteraciones hemodinámicas que se observan luego de la depleción de volumen sanguíneo. Objetivo El objetivo del presente trabajo fue evaluar la participación del sistema del óxido nítrico (NO) mitocondrial en la respuesta adaptativa del sistema cardiovascular ante un shock hipovolémico en ratas anestesiadas y no anestesiadas. Material y métodos El estudio se llevó a cabo con cuatro grupos de animales (n = 7 por grupo): grupo A, ratas control anestesiadas; grupo C, ratas control no anestesiadas; grupo AH, ratas anestesiadas sometidas a una hemorragia (20% de la volemia) y grupo CH, ratas no anestesiadas sometidas a una hemorragia. Se evaluaron el consumo de oxígeno, la actividad funcional de la NOS mitocondrial (mtNOS) y la producción mitocondrial de NO. Resultados No se observaron diferencias significativas entre los valores de control respiratorio en los distintos grupos estudiados. La actividad funcional de la mtNOS fue menor en el grupo AH respecto del grupo A (12 ± 2 y 19 ± 1, respectivamente). Este efecto fue de menor magnitud cuando la hemorragia se provocó en animales no anestesiados (17 ± 1 y 20 ± 1, respectivamente). La producción mitocondrial de NO disminuyó en los grupos sometidos a una pérdida aguda de sangre, tanto no anestesiados como anestesiados, respecto de los animales controles. Conclusiones El sistema del NO mitocondrial estaría involucrado en la respuesta de adaptación del sistema cardiovascular frente a la depleción aguda de volumen. Esta participación dependería del grado de anestesia del animal.

Background We have previously demonstrated that hypovolemia induced by acute bleeding is accompanied by a dynamic, heterogenous and time-dependent activation of the cardiac nitric oxide synthase (NOS). This system might be involved in the hemodynamic anomalies observed after blood volume depletion. Objective To assess the role of the mitochondrial nitric oxide (NO) system in the adaptive response of the cardiovascular system in anesthetized and non anesthetized rats under hypovolemic shock. Material and Methods Animals were divided in four groups (n=7 animals per group): Group A, anesthetized control rats; group C, non anesthetized control rats; group AB, anesthetized rats subjected to bleeding (20% of blood volume), and group CB, non anesthetized rats subjected to bleeding. Oxygen consumption, functional activity of mitochondrial NOS (mtNOS) and mitochondrial production of NO were assessed. Results There were no significant differences in the values of respiratory parameters among the different study groups. Group AB had less functional activity of mtNOS compared to group A (12±2 and 19±1, respectively). This effect was even lower in non anesthetized animals subjected to bleeding (17±1 and 20±1, respectively). Mitochondrial production of NO decreased in anesthetized and non anesthetized animals with acute bleeding compared to controls. Conclusions Mitochondrial NO system might be involved in the adaptive response of the cardiovascular system under acute volume depletion, depending on the animal's degree of anesthesia.

Polyphenols and red wine as antioxidants against peroxynitrite and other oxidants

The antioxidant capacity of polyphenols (+)-catechin, (-)-epicatechin and myricetin, and of different types of red wines (Cabernet Sauvignon, Malbec and blended wine) was evaluated by three assays. (a) NADH oxidation by peroxynitrite (ONOO-): the ONOO- scavenging activity was higher for myricetin (IC50=35 µM) than for (+)-catechin (IC50=275 µM) and (-)-epicatechin (IC50=313 µM). (b) Peroxynitrite initiated chemiluminescence in rat liver homogenate: (-)-epicatechin (IC50=7.0 µM) and (+)-catechin (IC50=13 µM) were more potent than myricetin (IC50=20 µM) in inhibiting the chemiluminescence signal. (c) Lucigenin chemiluminescence in aortic rings: (-)-epicatechin (IC50=15 µM) and (+)-catechin (IC50=18 µM) showed higher antioxidant capacity than myricetin (IC50=32 µM). All the assayed red wines were able to scavenge the oxidants and free radical species that generate the signal in each assay. Cabernet Sauvignon was the red wine with the highest antioxidant capacity in comparison with Malbec and blended wine. It is concluded that the use of sensitive biological systems (as the aortic ring chemiluminescence) provides important information in addition to the results from chemical (NADH oxidation by peroxynitrite) and biochemical (homogenate chemiluminescence) assays and offers advances in the physiological role of polyphenols.

Biochemistry of free radicals: from electrons to tissues

Free radicals are chemical species with an unpaired electron in the outer valence orbitals. The unpaired electron makes them paramagnetic (physics) and relatively reactive (chemistry). The free radiclas that are normal metabolites in aerobic biological systems have varied reactivities, ranging from the high reactivity of hydroxyl radical (t(1/2) = 10(-9) s)) to the low reactivity of melanins (t (1/2) = days)). The univalent reduction of oxygen that takes place in mammalian organs produces superoxide radicals at a rate of about 2 per cent of the total oxygen uptake. The primary production of superoxide radicals sustains a free radical chain reaction involving a series of reactive oxygen species (hydrogen peroxide, hydroxyl and peroxyl radical and singlet oxygen). Nitric oxide is almos tunreactive as free radical except for its termination reaction with superoxide radical to yield the strong oxidant peroxynitrite. Nitric oxide also reacts with ubiquinol in a redox reaction, with cytochrome oxidase competitively with oxygen, and oxymyoglobin and oxyhemoglobin displacing oxygen. Septic shock and endotoxemia produce muscle dysfunction and oxidative stress due to increased steady state concentrations of reative oxygen and nitrogen species.

Lipoic accid and the prevention of oxidative damage

Alpha-Lipoic acid is involved in the oxidative decarboxylation of ketoacids as a constituent of enzyme complexes in which it is covalently bound to the epsilon- amino group of lysine residues. It is employed as a therapeuthic agent in alcoholic and diabetic polyneuropathies and in chronic and toxic liver damage. Lipoic acid is effective in preventing oxidative damage in a series of oxidative stress situation. In vivo lipoic acid treatment (100 mg/kg) inhibited chemiluminescence overshoot after ischemia-reperfusion in the rat intestine. lipoic acid (50 to 150 mg/kg) also inhibited xanthine dehydrogenase to xanthine oxidase conversion in rat intestine homogenate. In vitro, lipoic acid inhibited buttermilk and rat liver xanthine oxidase activity and xanthine dehydrogenase to xanthine oxidase conversion in rat liver and intestine homogenates. Lineweaver-Burk and Dixon plots indicate that lipoic acid is a competitive inhibitor of xanthine oxidase with respect to xanthine.

Estudio comparativo de tres soluciones cardiopléjicas en pacientes sometidos a cirugía cardíaca / Comparative study of three cardioplegic solutions in patients submitted to cardiac surgery

Veinte pacientes operadores de cirugía de by pass aortocoronario fueron divididos en grupo I (n=7), que recibió como protección miocárdica una solución cardiopléjica standard; grupo II (n=6), que recibió una solución cardiopléjica conteniendo manitol; y grupo III (n=7) que recibió solución cardiopléjica con deferoxamina. Se tomaron biopsias de miocardio, previo al período isquémico (muestras A o preisquémicas) y a los 10 minutos de la reperfusión (muestras B o de reperfusión) las cuales fueron procesadas para quimioluminiscencia para detectar actividad de radicales libres y para microscopía electrónica con el objeto de evaluar lesión miocárdica a nivel de ultraestructura. Se observó que en el grupo I se producía un significativo aumento de los valores de quimioluminiscencia en las muestras B y ésto se asociaba con la presencia de áreas con franco edema mitocondrial. En los grupos II y III no había diferencia significativa entre las muestras A y B. Los resultados sugieren que durante la reperfusión se produce un daño miocárdico que en parte es causado por la citotoxicidad de los radicales libres del oxígeno. Se concluye además que la deferoxamina y más el manitol reducen las lesiones de reperfusión y que su mecanismo de acción sería por la capacidad antioxidante que poseen ambas sustancias

Lipoperóxidaçäo hepática e renal em ratos tratados com hexaclorociclohexano técnico / Hepatic and renal lipid peroxidation in rats treated with technical hexachlorocyclohexane

Ratos machos Wistar com 30 dias de idade receberam, por 60 a 90 dias, 900 ppm de hexaclorociclohexano técnico (HCH) na dieta. A lipoperoxidaçäo hepática e renal foi avaliada, determinando-se a quantidade de malonildialdeído produzida por homogenados de fígado e rim. A proliferaçäo do retículo endoplasmático agranular foi acompanhada pela medida dos níveis de citocromos P450 e b5. Encontrou-se um aumento significativo (68% e 39%, para 60 a 90 dias respectivamente) na produçäo hepática de lipoperóxidos, assim como no rim (25% e 46%). Os níveis hepáticos dos citocromos P450 e b5 mostraram-se aumentados em todos os casos. Possíveis mecanismos envolvidos säo discutidos