Effects of hemodialysis on guanidinopropionic acid metabolism.

Blood levels of guanidinopropionic acid (GPA), a putative uremic toxin, have been evaluated in 5 uremic patients before a dialytic session, at the end of it and during the following 68 h. GPA levels are markedly higher in uremic patients than in controls and are significantly reduced at the end of dialysis even if still higher than in controls. The clearance of GPA is similar to those of urea and creatinine, even if at the end of the dialysis session the percent decrease of GPA is significantly lower than that of urea. During the first 8 h after the end of dialysis GPA levels increase steeply; subsequently, the rate of accumulation of GPA in blood declines markedly remaining constant until the 68th hour. In conclusion GPA is markedly increased in blood of uremic patients and is significantly removed by dialysis. The evaluation of GPA increase per hour after the end of dialysis may provide an estimation of GPA production in uremic patients.