RESUMO
BACKGROUND: Dialyzed patients are chronically in a state of negative nitrogen balance, and amino acids, their building stones, are also significantly affected by dialysis. The purpose of the present investigation was to assess whether they should be supplied, how frequently and for how long and how they are influenced by the usual diet of patients. METHODS AND RESULTS: The examination was made in a group of 13 patients included in a regular haemodialysis programme. Their mean age was 53.2 +/- 12.4 years, they were dialyzed for an average period of 55 months, maximum 163 months. The patients were dialyzed three times per week for four hours, bicarbonate dialysate was used. The patients' diet was not modified in any way. A total of 52 haemodialysis were examined: losses of alpha-amino nitrogen were monitored as well as changes of serum concentrations of different amino acids. Their mean losses were 119 +/- 54.69 mmol/4 h: this corresponds to 10.5 +/- 4.8 mg amino acids. The dialysis clearance was on average 122.7 +/- 63.2 ml/min. This value did not differ significantly from the dialysis clearance of urea, but it was significantly higher than creatinine clearance (p < 0.05). During dialysis a significant drop (p < 0.001) of the plasma concentration of amino nitrogen occurred, however, the changes of serum concentrations of amino acids differed. A significant drop was recorded in serum concentrations of histamine, lysine, cysteine, methionine, tyrosine, glycine, asparagine, citrullin, glutamine, taurine. Before the beginning of dialysis the values of valine, lysine, threonine, serine, alanine and asparagine were lower than corresponds to the reference interval in healthy subjects. CONCLUSIONS: Changes of serum concentrations of individual amino acids are significantly influenced not only by their losses into the dialysate but also by their shift from cells into the extracellular fluid and by resorption from the digestive tract during protein intake in the course of dialysis. An adequate supply of high quality protein can compensate for these losses. Investigation of serum concentration of individual amino acids does not record their kinetic changes but can give an idea on the effectiveness of the dietary regime.