Nitrogenous Compounds in Hemodialysate

Abstract

Correlation of clinical and chemical changes in patients with uremia has not been possible for substances other than urea and electrolytes. Since clinical improvement is frequently seen following hemodialysis, examination of the dialysate for substances of possible importance seemed warranted. With use of the Kiil artificial kidney, small volumes of dialysate have been obtained and found suitable for analytical studies. Amino acid analyses performed after salt removal revealed a preponderance of acidic amino acids and 35 to 38 unknown ninhydrin reactive peaks. Following acid hydrolysis, the unknown peaks decreased in height and known amino acids increased, indicating a degradation of peptides or conjugated amino acids. Elution from the internal volume of Sephadex G-25 columns suggested molecular weights of less than 4000. Confirmatory evidence of low molecular weights was obtained in vitro by estimation of ninhydrin and Folin-Lowry phenol reactive materials remaining in the dialysant compared to glucose and urea. These results suggested that besides free amino acids, the nitrogenous compounds in the dialysate include conjugated amino acids or very small peptides. Of additional interest in one patient was the decrease in removal of some amino acids and other nitrogenous materials from the first to the eighth clinical dialysis, suggesting a relationship to progressive malnutrition observed in this case.