Plasma and muscle free amino acids in uremia: influence of nutrition with amino acids.

Untreated uremic patients show grossly abnormal amino acid patterns with low concentrations of threonine, valine, tyrosine and lysine in muscle and plasma and low plasma concentrations of isoleucine, leucine and phenylalanine. Patients who had been treated for more than 10 weeks with a low protein diet, providing 16-20 g protein/day (LPD), supplemented with an essential amino acid preparation which contained 2-3 times the minimum requirements for normal man [Rose 1949] + histidine (EAAH), still had valine concentrations in plasma and muscle which were reduced by 40-45% and still showed the abnormal distribution of leucine and isoleucine with low plasma and normal muscle concentrations. The muscle concentration of tyrosine was decreased by 45%, whereas the plasma concentration was normal. In 8 patients treated for a mean period of 115 days with LPD supplemented with a new amino acid formula, with a higher proportion of valine and with the addition of tyrosine (NAAF), the depletion of valine in plasma and muscle was completely corrected but the intracellular tyrosine concentration was not fully normalized. The results show that the essential amino acid abnormalities in plasma and muscle that occur typically in uremia can be corrected by nutritional means, and that uremic patients may require amino acids in other proportions than healthy subjects. The results also suggest that normalization of amino acid pools may improve nitrogen utilization. Our observation of markedly decreased i.c. tyrosine concentration after treatment with LPD + EAAH is in support of the indispensability of tyrosine in uremia. The failure to fully correct muscle tyrosine with NAAF suggests that proportionally more tyrosine should be provided.