Analysis of neurochemicals by capillary electrophoresis in athletes' urine and a pilot study of their changes responding to sport fatigue

Abstract

Neurochemicals may play an important role in metabolism and sport fatigue. In order to investigate the potential links, a simple, rapid, and accurate analytical method, capillary zone electrophoresis (CZE), capable of carrying out a simultaneous separation of 11 neurochemicals has been developed and validated. The 11 analytes included neurotransmitter precursors: arginine (Arg) and tyrosine; neurotransmitters: serotonin (5-HT), dopamine (DA), and epinephrine (EP); neurotransmitter metabolites: 5-hydroxy-3-indoleacetic acid (5-HIAA), homovanillic acid (HVA), and vanilla mandelic acid (VMA); matrix components of urine: creatinine (Cre), uric acid, and acetoacetic acid. They could be well separated within 7 min at a separation voltage of +25 kV and 12.5 mmol L⁻¹ Na₂B₄O₇ (pH = 9.9) was selected as the running buffer. The proposed method allowed the limits of detection of urinary metabolites to be in the range of 0.04–1.50 μmol L⁻¹ (S/N = 3) and the RSDs of migration time were 0.09–0.91%. For three models of physiological status: normal, fatigue, and relaxed, to establish an athlete model of fatigue, the athletes continued to ride a bike for 45 minutes; we selected the RPE (ratings of perceived exertion) scale for evaluation of the extent of fatigue, and the RPE values are more than 18 in the model of fatigue of 5 athletes. In this study, we found that Arg was lower, 10.6–62.2%, in urine of sport fatigue compared with normal and relaxed states and the excretion of HVA increased 2.75–36.42% after sport fatigue. This method can be used for potential applications involving the determination of two biomarker compounds for the rapid diagnosis of fatigue models.