TOTAL, FREE, AND PROTEIN-BOUND SULFUR AMINO-ACIDS IN UREMIC PATIENTS

Fasting plasma concentrations of sulphur amino acids (sAA) were measur ed in nine non-dialysed (ND) chronic uraemic patients on conservative treatment, 10 patients on continuous ambulatory peritoneal dialysis (C APD), nine patients on haemodialysis (HD) treatment, and 10 healthy su bjects (HS). Methionine and taurine concentrations were significantly decreased in the CAPD and HD patients and tended to be low in the ND p atients. Cysteine sulphinic acid (CSA) levels were significantly highe r in all patient groups. Total (t), free (f), and protein-bound (pb) h omocysteine (Hey) and cysteine (Cys) were significantly increased in a ll patient groups. Serine, a substrate for cystathionine synthesis fro m Hey, showed significantly lower concentrations in all patient groups . The percentages of pbHcy were significantly higher in the CAPD and H D patients than in the ND patients (P < 0.0001, P = 0.002 respectively ) or in the HS (P < 0.0001, P = 0.008 respectively), whereas the perce ntages of pbCys in CAPD and HD patients were significantly higher than in ND patients (P = 0.0006, P = 0.009 respectively) and tended to be high without reaching statistical significance compared to the HS. A s ingle HD treatment decreased tHcy by 26%, fHcy by 39%, and pbHcy by 22 %, as well as tCys by 40%, fCys by 54%, and pbCys by 27%. The tHcy con centration, although decreased by HD treatment, remained higher than i n HS. whereas tCys was normalized by the dialysis session. In addition , PID treatment significantly decreased the plasma concentrations of m ethionine, CSA, taurine, and serine. We conclude that, except for meth ionine and taurine, the plasma sAA in their different forms are marked ly increased in dialysed and non-dialysed uraemic patients. The percen tages of pbHcy and pbCys were significantly higher in dialysed than in ND uraemic patients. HD treatment can normalize the tCys concentratio n, and decrease the tHcy concentration but not normalize it. The obser ved hyperhomocysteineaemia and low taurine levels may contribute to th e high incidence of cardiovascular disease in uraemic patients.