Determination of serum aromatic amino acid in patients with CRI by high performance liquid chromatography with fluorescence detection

Abstract

Objective A HPLC-FLD method was developed to determine the levels of serum AAA in CRI patients, and to study the variation of serum AAA in CRI patients and its clinical significances. MethodsSerum samples were collected from 100 health controls and 80 CRI patients. According to 2002 National Kidney Foundation (NKF) staging diagnosis, CRI patients included 4 of stage 2, 12 of stage 3, 12 of stage 4, 52 of stage 5. According to pathogenesis, CRI patients were also divided into 3 groups :chronic nephritis group ( n = 32), DM group ( n = 36), hypertension group ( n = 12 ).Serums were deproteinized by equal volume of 5％ (v/v) PCA and supernate were analyzed direcdy. External standard method was used as quantitative method. The analytical column was Megres C18. 10％ acetonitrile in water was used as mobile phase. Flow rote was 1.0 ml/min. The wavelengths of fluorescence excitation and emission were changed with specific time. The levels of Tyr, Phe and Trp in CRI groups, different CKD stages and different pathogenesis were compared with healthy control groups to evaluated the sensitivity and specificity of serum AAA for CRI diagnosis. Results The linear ranges of the method were 0. 550 -275.000, 3. 050 - 1220. 000 and 0. 049 -49. 000 pμmol/L for Tyr, Phe and Trp, respectively. The limit of detection (LOD) was 0.014 μmol/L for Tyr, 0.500μmol/L for Phe, and 0.005 μmol/L for Trp. The average recovery was 100. 9％, 101.3％ and 98. 5％ for Tyr, Phe and Trp, respectively. Intra-day CVwas 3. 18％ -4. 20％ ( mean was 3. 13％ )and inter-day CV was 3. 18％ -4. 20％ ( mean was 3. 58％ ). The concentration of serum AAA, Tyr and Trp and the ratio of Tyr/Phe in CRI patients were( 135.74 ±23.23 )μmol/L, (52.27 +8.25) μmol/L, (21.49 ±4.25) μmol/L and[0.87(0.68 - 1.05)]μmol/L. which were lower than that in healthy groups (t value was -14. 709, 4.452, 22. 100, U value was 266.000,respectively, P＜0. 05). The concentration of serum AAA, Tyr and Trp and the ratio of Tyr/Phe in healthy groups were ( 174. 47 ± 11.57 ) μmol/L, ( 63.53 ± 4. 68 ) μmol/L, (44. 22 ± 3. 67 ) μmol/L and[0. 97(0. 94 - 1.00)]μmoL/L. There were no statistically significant difference between the different stage of CRI. Compared with the concentration of Tyr, Phe and Trp among chronic nephritis group, DM group,hypertension group, the concentration of Tyr had no significant changes among these three kinds of diseases (P ＞ 0. 05 ). The concentration of Phe had significant changes between Chronic nephritis group and DM group, Chronic nephritis group and hypertension group ( U = 395.00, 114. 00, P ＜ 0. 05 ) ; the concentration of Trp haad significant changes between Chronic nephritis group and DM group ( U = 349.00, P ＜ 0. 05 ).The diagnostic sensitivity and specificity of serum AAA for CRI were 90％ (72/80) and 100. 0％ (100/100).Conclusions The method of high-performance liquid chromatography with fluorescence detection ( HPLC-FLD) is simple, rapid, sensitive and specific. Simultaneous determination of serum AAA was benefit to the diagnosis and evaluation of CRI patients. Key words: Renal insufficiency, chronic; Amino acids, aromatic; Chromatography, high pressure liquid