RESUMO
Citrullinemia is an inborn error of the urea cycle caused by deficient argininosuccinate synthetase, which leads to accumulation of L-citrulline and ammonia in tissues and body fluids. The main symptoms include convulsions, tremor, seizures, coma, and brain edema. The pathophysiology of the neurological signs of citrullinemia remains unclear. In this context, we investigated the in vitro effects of L-citrulline and ammonia in cerebral cortex from 30-day-old rats on oxidative stress parameters, namely thiobarbituric acid-reactive substances (TBA-RS), chemiluminescence, mitochondrial membrane protein thiol content, intracellular content of hydrogen peroxide, total radical-trapping antioxidant potential (TRAP), total antioxidant reactivity (TAR) as well as on the activities of the antioxidant enzymes (catalase, superoxide dismutase, and glutathione peroxidase). L-Citrulline significantly diminished TRAP (26%) and TAR (37%), while ammonia decreased TAR (30%). Ammonia increased SOD activity (65%) and L-citrulline did not affect the activities of any antioxidant enzymes. We also observed that L-citrulline and ammonia did not alter lipid peroxidation parameters, levels of hydrogen peroxide, and mitochondrial membrane protein thiol content. Taken together, these results may indicate that L-citrulline and ammonia decreased the antioxidant capacity of the brain, which may reflect a possible involvement of oxidative stress in the neuropathology of citrullinemia.
Assuntos
Amônia/farmacocinética , Antioxidantes/metabolismo , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/metabolismo , Citrulina/farmacocinética , Citrulinemia/metabolismo , Animais , Catalase/metabolismo , Citrulina/sangue , Ativação Enzimática/efeitos dos fármacos , Glutationa Peroxidase/metabolismo , Peróxido de Hidrogênio/metabolismo , Técnicas In Vitro , Peroxidação de Lipídeos/efeitos dos fármacos , Peroxidação de Lipídeos/fisiologia , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/fisiologia , Ratos , Ratos Wistar , Compostos de Sulfidrila/metabolismo , Superóxido Dismutase/metabolismo , Substâncias Reativas com Ácido Tiobarbitúrico/metabolismoRESUMO
OBJECTIVE: In previous studies we demonstrated that the administration of furosemide associated with L-arginine contributes to enhanced hypotension and induces greater water than electrolyte excretion, in both normal and expansion conditions. The aim of the present study was to elucidate the interaction between furosemide and the nitric oxide (NO) system in renal and vascular responses during extracellular volume expansion. DESIGN AND METHODS: Expanded [10% body weight (bw)] and non-expanded anaesthetized male Wistar rats were treated with furosemide (7.5 mg/kg bw). Mean arterial pressure, nitrite and nitrate excretion (NOx) were determined. NADPH-diaphorase activity, a marker of nitric oxide synthase (NOS) activity, was measured histochemically in different segments of the nephron, aorta and renal arteries. NOS activity was determined using an L-[U14C]-arginine substrate in the kidney and aorta of expanded and non-expanded rats, in basal conditions and after furosemide (10 micromol/l). RESULTS: The hypotensive effect of furosemide was enhanced when NO production was stimulated in expanded and non-expanded animals. The diuretic treatment induced a significant increase in NOx excretion, in NADPH-diaphorase activity in the thick ascending limb of Henle, renal arteries and aorta, and in NOS activity in aorta and kidney in both groups. CONCLUSIONS: Our results suggest that the hypotensive effect of furosemide may be attributed to NO-mediated vasodilation. The enhanced NOS activity, observed in the renal artery of furosemide-treated rats, could explain the increased renal plasma flow induced by furosemide. In addition, NO-pathway stimulation in the kidney could be one of the mechanisms by which furosemide exerts its diuretic and natriuretic effects, in control and in expansion conditions.
Assuntos
Diuréticos/farmacologia , Furosemida/farmacologia , Hipotensão/metabolismo , Rim/metabolismo , Óxido Nítrico/metabolismo , Animais , Pressão Sanguínea/efeitos dos fármacos , Volume Sanguíneo/fisiologia , Radioisótopos de Carbono , Citrulina/farmacocinética , Diurese/efeitos dos fármacos , Líquido Extracelular/metabolismo , Rim/irrigação sanguínea , Rim/efeitos dos fármacos , Masculino , NADPH Desidrogenase/metabolismo , Natriurese/efeitos dos fármacos , Nitratos/urina , Óxido Nítrico Sintase/metabolismo , Nitritos/urina , Ratos , Ratos Wistar , Circulação Renal/efeitos dos fármacosRESUMO
General amino acid permease (GAP1) activity was evaluated in adenylate cyclase-deficient Saccharomyces cerevisiae to determine the effect of cAMP levels on GAP1 activity. Lowering cAMP concentrations in the culture media led to a decrease in the initial rates of L-citrulline uptake. Kinetics of the amino acid transport system showed a partial loss of transport capacity, with no apparent modifications in permease affinity.
Assuntos
AMP Cíclico/farmacologia , Proteínas de Membrana Transportadoras/metabolismo , Saccharomyces cerevisiae/metabolismo , Sistemas de Transporte de Aminoácidos , Transporte Biológico/efeitos dos fármacos , Citrulina/farmacocinética , CinéticaRESUMO
L-leucine entrance into Saccharomyces cerevisiae is mediated by the general amino acid permease, GAP and two transport systems, S1 and S2, kinetically characterized. S1 is a high-affinity, low-velocity transport system, operating at lower L-leucine external concentration (0.05-0.1 mM), while S2 is a low-affinity, high-velocity transport system, operating at higher L-leucine external concentration (1.0 mM). In cells grown in minimal medium containing ammonium as sole nitrogen source the values of L-leucine entrance and uptake are smaller than those in cells grown in L-proline containing medium. When GAP is repressed by ammonium, L-leucine entrance is mediate by systems S1 and S2. Both systems are inhibited by ammonium. When GAP is derepressed, in cells grown in L-proline medium, L-leucine is transported by systems S1 and GAP (lower L-leucine external concentration), and mainly by S2 (higher L-leucine external concentration). GAP is the largest system inhibited by ammonium.
Assuntos
Sulfato de Amônio/farmacologia , Proteínas Fúngicas/antagonistas & inibidores , Leucina/farmacocinética , Moduladores de Transporte de Membrana , Proteínas de Membrana Transportadoras/antagonistas & inibidores , Saccharomyces cerevisiae/efeitos dos fármacos , Sistemas de Transporte de Aminoácidos , Transporte Biológico/efeitos dos fármacos , Citrulina/farmacocinética , Proteínas Fúngicas/metabolismo , Cinética , Proteínas de Membrana Transportadoras/metabolismo , Prolina/metabolismo , Saccharomyces cerevisiae/metabolismoRESUMO
En Saccharomyces cerevisiae la entrada de L-leucina es mediada por la permeasa general de aminoácidos, GAP, y dos sistemas cinéticamente caracterizados, uno de alta afinidad y baja velocidad, S1, para concentraciones externas de L-leucina 0,05-01mM y otro de baja afinidad, alta velocidad, S2, para concentraciones externas 1.0mM. En células crecidas en medios suplementados con amonio, como única fuente de nitrógeno, los valores de entrada e incorporación son menores que en células crecidas en medios suplementados con L-prolina. En condiciones de represión de la GAP por iones amonio, la entrada de L-leucina es mediada por los sistemas S1 y S2. Los dos sistemas son parcialmente inhibidos por efecto de iones amonio. En condiciones de depresion de la GAP, por crecimiento en L-prolina, la entrada de L-leucina es mediada por los sistemas S1 y GAP, bajas concentraciones externas de L-leucina mediada por centraciones externas. El amonio inhibe en mayor extensión la entrada de L-leucina mediada por La GAP
Assuntos
Sulfato de Amônio/farmacologia , Leucina/farmacocinética , Proteínas de Membrana Transportadoras/antagonistas & inibidores , Proteínas Fúngicas/antagonistas & inibidores , Saccharomyces cerevisiae/efeitos dos fármacos , Citrulina/farmacocinética , Cinética , Proteínas de Membrana Transportadoras/metabolismo , Prolina/metabolismo , Proteínas Fúngicas/metabolismo , Saccharomyces cerevisiae/metabolismo , Transporte BiológicoRESUMO
En Saccharomyces cerevisiae la entrada de L-leucina es mediada por la permeasa general de aminoácidos, GAP, y dos sistemas cinéticamente caracterizados, uno de alta afinidad y baja velocidad, S1, para concentraciones externas de L-leucina 0,05-01mM y otro de baja afinidad, alta velocidad, S2, para concentraciones externas 1.0mM. En células crecidas en medios suplementados con amonio, como única fuente de nitrógeno, los valores de entrada e incorporación son menores que en células crecidas en medios suplementados con L-prolina. En condiciones de represión de la GAP por iones amonio, la entrada de L-leucina es mediada por los sistemas S1 y S2. Los dos sistemas son parcialmente inhibidos por efecto de iones amonio. En condiciones de depresion de la GAP, por crecimiento en L-prolina, la entrada de L-leucina es mediada por los sistemas S1 y GAP, bajas concentraciones externas de L-leucina mediada por centraciones externas. El amonio inhibe en mayor extensión la entrada de L-leucina mediada por La GAP (AU)