RESUMO
PURPOSE: We investigated the effects of caffeine on the ammonia and amino acid metabolism of elite soccer players. METHODS: In this double-blind randomized study, athletes (n = 19) received 5 mg·kg caffeine or lactose (LEx, control) and performed 45 min of intermittent exercise followed by an intermittent recovery test (Yo-Yo IR2) until exhaustion. The caffeine-supplemented athletes were divided into two groups (CEx and SCEx) depending on their serum caffeine levels (<900% and >10,000%, respectively). Data were analyzed by ANOVA and Tukey post hoc test (P < 0.05 was considered to be statistically significant). RESULTS: Caffeine supplementation did not significantly affect the performance (LEx = 12.3 ± 0.3 km·h, 1449 ± 378 m; CEx = 12.2 ± 0.5 km·h, 1540 ± 630 m; SCEx = 12.3 ± 0.5 km·h, 1367 ± 330 m). Exercise changed the blood concentrations of several amino acids and increased the serum concentrations of ammonia, glucose, lactate, and insulin. The LEx group showed an exercise-induced increase in valine (â¼29%), which was inhibited by caffeine. Higher serum caffeine levels abolished the exercise-induced increase (â¼24%-27%) in glutamine but did not affect the exercise-induced increase in alanine (â¼110%-160%) and glutamate (42%-61%). In response to exercise, the SCEx subjects did not exhibit an increase in uremia and showed a significantly lower increase in their serum arginine (15%), citrulline (16%), and ornithine (ND) concentrations. CONCLUSIONS: Our data suggest that caffeine might decrease systemic urea by decreasing the glutamine serum concentration, which decreases the transportation of ammonia to the liver and thus urea synthesis.
Assuntos
Aminoácidos/sangue , Atletas , Cafeína/farmacologia , Exercício Físico/fisiologia , Futebol/fisiologia , Uremia/prevenção & controle , Amônia/sangue , Análise de Variância , Cafeína/sangue , Método Duplo-Cego , HumanosRESUMO
Capillary electrophoresis coupled to inductively coupled plasma mass spectrometry was used in a speciation study on disodium monomethylarsonate (DS-MMA(V)) and its metabolites in horses, to which the drug was administered by intramuscular injection on five consecutive days at a single arsenic dosage of 270 mg day(-1). Samples of urine, whole blood, plasma, and mane hair were analyzed before, during, and after drug administration. The data show that blood clearing and urinary excretion of MMA is a fast process following first-order kinetics with biological half-lives of about 38 h and 44 h for urine and plasma, respectively. In the time period of 9 days studied, the only metabolite detected in urine was dimethylarsinic acid (DMA(V)), which 4 days after the last drug administration accounted for up to 75% of the total excreted arsenic species. This shows, for the first time, that biomethylation of MMA(V) to DMA(V) is the principal metabolic pathway of this drug in horses. Although DS-MMA(V) was administered only during a short 5-day period, an up to six fold increase of arsenic could be measured in the newly grown mane hair.
Assuntos
Arsenicais/sangue , Arsenicais/urina , Animais , Arsênio/administração & dosagem , Arsênio/análise , Arsenicais/metabolismo , Ácido Cacodílico/metabolismo , Ácido Cacodílico/urina , Eletroforese Capilar , Cabelo/química , Cavalos , Injeções Intramusculares , Espectrometria de Massas/métodos , Metilação , Sensibilidade e Especificidade , Fatores de TempoRESUMO
O uso de ensaios imunoenzimáticos tipo Elisa (Enzyme Lynked Immunosorbent Assay), largamente utilizado em laboratórios de controle de dopagem, é aceito apenas como método de triagem, havendo portanto, a necessidade de uma técnica mais apurada para confirmação. Devido à grande sensibilidade da técnica ELISA em relação às análises por CG/EM, torna-se necessária a determinação de um valor, que na técnica ELISA corresponda à menor concentração detectável detectável no método de confirmação no método de confirmação, facilitando com isto a seleção das amostras suspeitas. O presente trabalho tem como objetivo definir este valor, à partir do qual a amostra será submetida à técnica de Cromatografia a Gás com Espectrometria de Massa (CG/EM). Este limite de decisão empregado na técnica Elisa, irá minimizar o custo operacional, pois apenas as amostras que apresentem valores acima deste limite serão submetidas ao método de confirmação.