Effect of hemodialysis on protein synthesis

<(Background)under bar>: Earlier studies have shown that hemodialysis (HD) treatment stimulates net protein catabolism. Several factors associated wit h KD affect protein catabolism, such as an inflammatory effect due to blood -membrane contact and loss of amino acids and glucose into the dialysate. < (Subjects, material and methods)under bar>: We have studied protein synthes is in skeletal muscle of healthy volunteers (n = 9) before and after a sing le heparin-free HD. Protein synthesis (PS) was studied, using 2 independent techniques: the incorporation of labeled H-2(5)-phenylalanine into muscle protein, which gives a quantitative measure of the fractional synthesis rat e of muscle proteins, and the concentration and size distribution of riboso mes, which gives a qualitative estimate of protein synthesis. Furthermore, free amino acid concentrations were determined in muscle and plasma. <(Resu lts)under bar>: The rate of PS, expressed as the fractional synthesis rate, decreased by 13% during HD (p < 0.02). The capacity for PSI as reflected b y the total concentration of ribosomes. was reduced by 22% (p < 0.02) and t he activity of PS, expressed as the relative proportion of polyribosomes, d ecreased from 48.4 +/- 0.9% to 44.8 +/- 0.8% after dialysis (p < 0.01). The re was a total loss of 5.8 +/- 0.3 g amino acid to the dialysate. Plasma an d muscle free amino acid concentrations were determined at four time points ; before and after the phenylalanine incorporation period, before dialysis and before and after the second incorporation period after dialysis. Immedi ately after dialysis, there was a decrease in plasma asparagine, histidine, alanine, taurine, valine and tryptophane. In muscle, no changes occurred e xcept for a slight increase in leucine after dialysis. In blood, the glucos e concentration decreased and the total amount of glucose lost to the dialy sate was 21 +/- 3.0 g. In summary, one single hemodialysis treatment decrea ses fractional protein synthesis rate in skeletal muscle. <(Conclusion)unde r bar>: The results demonstrate substantial losses of amino acids and gluco se to the dialysate and decreased amino acid concentrations in plasma, but only minimal changes in the intracellular amino acid concentrations in musc le, suggesting that the decreased PS is caused not by lack of amino acid pr ecursors at the site of the synthesis activity, but by other mechanisms.