RESUMEN
BACKGROUND AND AIMS: Cystinosis is an inborn error of metabolism, clinically characterised by severe renal involvement and development of corneal cystine deposits, especially in the adult form of the disease. Cystinosis is a treatable condition. Therefore, an early diagnosis is necessary to start therapy. For biochemical confirmation of the condition it is necessary to quantify intracellular cystine concentrations. For this, different methods have been described with variations in cell isolation strategies and the amino acid quantification techniques used. In order to improve confirmatory biochemical diagnosis in our setting, a protocol for intraleukocitary cystine quantification was established. METHODS: A high performance liquid chromatography based method for cystine quantification in polymorphonuclear cells was implemented. Evaluation of the best anticoagulant to use and temperature stability of the sample at 4ÌC were performed. In addition, we established reference values for our population. RESULTS: It was determined that intraleukocitary cystine quantification must be performed in blood samples containing acid-citrate-dextrose as anticoagulant. Samples must be processed immediately due to their poor stability even when refrigerated. Based on the results from 50 healthy individuals, the cut-off point established for our population was 0.34nmol 1/2 cystine/mg. CONCLUSION: The adaptation performed to the cystine quantification method here presented the highest control population that has been reported in the literature so far. Our results highlight the need for making available a cystine quantification method locally and confirm the convenience for each laboratory to establish its own reference values to provide greater reliability for interpreting results.
Asunto(s)
Cistina/sangre , Cistinosis/diagnóstico , Neutrófilos/química , Anticoagulantes , Cromatografía Líquida de Alta Presión , Ácido Cítrico , Frío , Colombia , Síndrome de Fanconi/etiología , Glucosa/análogos & derivados , Humanos , Valores de ReferenciaRESUMEN
BACKGROUND/AIMS: Oxidative stress has been considered a nontraditional risk factor for cardiovascular disease in the chronic kidney disease (CKD) population, possibly triggered by uremic toxicity. METHODS: A chromatographic method with coulometric detection was adapted to directly and simultaneously determine cysteine (Cys) and cystine (Cyss) in plasma samples. Healthy subjects and CKD subjects in different stages were analyzed. The free Cys and free Cyss levels in their plasma were determined, and the reduction potential [Eh(Cyss/2Cys)] was calculated with the Nernst equation. RESULTS: Healthy plasma presented Eh(Cyss/2Cys) of -123 ± 7 mV. Plasma Eh(Cyss/2Cys) correlated significantly with creatinine levels (p < 0.0001, r = 0.62). CONCLUSION: Plasma Eh(Cyss/2Cys) correlated with increased levels of plasma creatinine, supporting the view that uremia triggers oxidative stress. In addition, it may be used as a quantitative oxidative stress biomarker in uremic conditions.
Asunto(s)
Creatinina/sangre , Cisteína/sangre , Cistina/sangre , Insuficiencia Renal Crónica/sangre , Adolescente , Adulto , Anciano , Biomarcadores/sangre , Cromatografía Líquida de Alta Presión , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estrés Oxidativo , Adulto JovenRESUMEN
OBJECTIVE: Cystinosis causes renal and other organ failure. Treatment with 6-hourly cysteamine bitartrate (Cystagon, Mylan, Morgantown, West Virginia) reduces intracellular cystine and the rate of organ deterioration. A recent study showed that an enteric-release cysteamine required less frequent daily dosing. This report describes the long-term use of enteric-coated (EC) cysteamine bitartrate (Cystagon) in children with cystinosis. STUDY DESIGN: After a pharmacokinetic and pharmacodynamic study of EC-cysteamine in children with cystinosis, 5 patients remained on twice-daily treatment. White blood cell cystine levels were measured 12 hours after ingestion every 4 to 8 weeks. These levels were then compared with the patient's previous 6-h post-dose levels taken while on regular cysteamine bitartrate before entering the study. Blood chemistry was also measured. RESULTS: Five children with cystinosis (mean age, 9 years; range, 8 to 17 years) who previously took cysteamine bitartrate (mean dose, 47 mg/kg body wt), received EC-cysteamine for 10 to 27 months (mean dose, 25 mg/kg body wt) and had mean white blood cell cystine levels of 0.77 and 0.71 nmol half-cystine/mg protein, respectively. During the study period, patients maintained adequate growth and there was no significant deterioration in renal or thyroid function. Two children were required to restart acid suppression after 6 months on EC-cysteamine therapy. CONCLUSIONS: Long-term, twice-daily EC-cysteamine, given at approximately 60% of the previous daily dose of cysteamine bitartrate, was effective at maintaining white blood cell cystine levels within a satisfactory range. There was no significant deterioration in renal or thyroid function.
Asunto(s)
Cisteamina/administración & dosificación , Cistinosis/tratamiento farmacológico , Adolescente , Niño , Creatinina/sangre , Cistina/sangre , Cistinosis/sangre , Esquema de Medicación , Femenino , Humanos , Leucocitos/metabolismo , Masculino , Comprimidos RecubiertosRESUMEN
Peaks corresponding to arg-vasotocin obtained by HPLC from Sep-Pak C18 column extracts of Bothrops jararaca plasma were identified by radioimmunoassay and amino acid analysis. Plasma vasotocin and protein levels, osmolality, and L-cystine-di-beta-naphthylamidase were also compared in snakes under normal hydration conditions with or without chronic administration of vasotocin or in the presence of chronic hydroosmotic challenges. Sep-Pak C18 and radioimmunoassay were validated for the extraction and determination of this peptide, respectively (about 80% recovery). EDTA presented a protective action on this recovery compared to the use of heparin as anticoagulant for snake blood. A reduction of vasotocin content related to the time of incubation of this peptide added to snake plasma was detected by radioimmunoassay. Snake plasma activity also on L-cystine-di-beta-naphthylamide indicated that this vasotocin-destroying effect was due to hydrolysis by a cystine-aminopeptidase-like activity. Plasma levels of vasotocin revealed an unexpected dispersion and absent correlation with plasma levels of osmolality. Measurable vasotocin in a large number of snakes associated with lower levels of l-cystine-di-beta-naphthylamidase in acute than in chronic salt loading suggested the role of this enzyme activity in long-term regulation of the vasotocin system in this snake.