ABSTRACT
Methylated arginine analogues are often used as probes of the effect of nitric oxide; however, their specificity is unclear and seems to be frequently overestimated. This study analyzed the effects of N G -methyl-L-arginine (L-NMMA) on the endothelium-dependent release of vascular superoxide radicals triggered by increased flow. Plasma ascorbyl radical signals measured by direct electron paramagnetic resonance spectroscopy in 25 rabbits increased by 3.8 ñ 0.7 nmol/l vs baseline (28.7 ñ 1.4 nmol/l, P<0.001) in response to papaverine-induced flow increases of 121 ñ 12 por cento. In contrast, after similar papaverine-induced flow increases simultaneously with L-NMMA infusions, ascorbyl levels were not significantly changed compared to baseline. Similar results were obtained in isolated rabbit aortas perfused ex vivo with the spin trap Ó-phenyl-N- tert -butylnitrone (N = 22). However, in both preparations, this complete blockade was not reversed by co-infusion of excess L-arginine and was also obtained by N-methyl-D-arginine, thus indicating that it is not related to nitric oxide synthase. L-arginine alone was ineffective, as previously demonstrated for N G -methyl-L-arginine ester (L-NAME). In vitro , neither L-arginine nor its analogues scavenged superoxide radicals. This nonspecific activity of methylated arginine analogues underscores the need for careful controls in order to assess nitric oxide effects, particularly those related to interactions with active oxygen species
Subject(s)
Animals , Male , Rabbits , Arginine/analogs & derivatives , Enzyme Inhibitors/pharmacology , Aorta, Thoracic/drug effects , Arteries/drug effects , Electron Spin Resonance Spectroscopy , Free Radicals , Papaverine/pharmacology , Vasodilator Agents/pharmacologyABSTRACT
A tuberculose osteoarticular representa cerca de 1 por cento do total de casos de tuberculose resgistrados no Estado do Rio Grande do Sul. Devido a sua infrequência, é pouco considerada pelo ortopedista, levando a marcado atraso no diagnóstico. Os autores apresentam um caso de bursite trocantérica tuberculosa e enfatizam a importância de avaliaçäo cuidadosa para esta doença nos pacientes com sintomas músculo-esqueléticos crônicos, incluindo os com bursite trocantérica resistentes ao tratamento conservador.