Plasma tryptophan level in chronic renal failure.

Total (Trp), free (fTrp) and bound (bTrp) tryptophan concentrations were measured in the plasma of hemodialyzed (HD), peritoneally dialyzed (CAPD) and conservatively treated (ND) patients in chronic renal failure (CRF). 1) A marked decrease of Trp and bTrp was found in all three groups of patients. 2) fTrp concentration was unaltered in the HD and CAPD groups but decreased in the ND patients. 3) No relationship between a fall of bTrp and plasma albumin and transferrin levels was found. 4) Decreased body weight was not reflected in changes in Trp, bTrp and fTrp. 5) An inverse correlation between the serum creatinine and the bTrp/albumin ratio was found. Two alterations of Trp metabolism in CRF may be outlined: Trp deficiency and an alteration of Trp binding to plasma albumin. They affect Trp availability and seem to correlate with the degree of kidney function impairment.