Résumé
ABSTRACT Considering that thiol-containing enzymes like kinases are critical for several metabolic pathways and energy homeostasis, we investigated the effects of cystine dimethyl ester and/or cysteamine administration on kinases crucial for energy metabolism in the kidney of Wistar rats. Animals were injected twice a day with 1.6 µmol/g body weight cystine dimethyl ester and/or 0.26 µmol/g body weight cysteamine from the 16th to the 20th postpartum day and euthanized after 12 hours. Pyruvate kinase, adenylate kinase, creatine kinase activities and thiol/disulfide ratio were determined. Cystine dimethyl ester administration reduced thiol/disulfide ratio and inhibited the kinases activities. Cysteamine administration increased the thiol/disulfide ratio and co-administration with cystine dimethyl ester prevented the inhibition of the enzymes. Regression between the thiol/disulfide ratio, and the kinases activities were significant. These results suggest that redox status may regulate energy metabolism in the rat kidney. If thiol-containing enzymes inhibition and oxidative stress occur in patients with cystinosis, it is possible that lysosomal cystine depletion may not be the only beneficial effect of cysteamine administration, but also its antioxidant and thiol-protector effect.
Sujets)
Animaux , Thiols , Mercaptamine/pharmacologie , Cystine/analogues et dérivés , Disulfures , Homéostasie/effets des médicaments et des substances chimiques , Rein/effets des médicaments et des substances chimiques , Adenylate kinase/analyse , Adenylate kinase/effets des médicaments et des substances chimiques , Reproductibilité des résultats , Rat Wistar , Creatine kinase/analyse , Creatine kinase/effets des médicaments et des substances chimiques , Cystine/pharmacologie , Agents de déplétion en cystine/pharmacologieRésumé
Diversos erros inatos do metabolismo, entre os quais a galactosemia, a homocistinúria, a doença de Lowe, as mucopolissacaridoses e as dislipidoses, podem levar à deficiência visual. A detecçäo desses distúrbios permite, em determinados casos, que afetados e familiares se beneficiem de medidas preventivas e/ou terapêuticas. Visando à identificaçäo de distúrbios metabólicos, 160 deficientes visuais foram estudados através de inúmeras técnicas bioquímicas de triagem e diagnóstico. Com o objetivo de testar a eficiência dos métodos de triagem empregados, 71 desses pacientes foram submetidos a uma reavaliaçäo cuidadosa. Em nenhum dos estudos foi detectados um erro inato do metabolismo relacionado com deficiência visual. Na avaliaçäo inicial foi identificado um caso de cistinúria. Na reavaliaçäo, esse diagnóstico foi confirmado e foram detectados distúrbios metabólicos intermitentes (glicosúria renal e frutosúria essencial) em 2 pacientes. Esses resultados indicam que a prevalência de erros inatos do metabolismo que têm manifestaçöes oculares é baixa em deficientes visuais, e que a triagem rotineira é eficiente para a detecçäo de anormalidades metabólicas persistentes