Metabolism of guanidino compounds in uremia

Study in CAPD patiets

Abstract

In order to study the metabolism of guanidino compounds (GCs) in 12 patients with chronic renal failure (CRF) under CAPD treatment, we observed the changes in serum GCs in relation to clinical manifestations and to acid-base balance during the course of CAPD treatment.We also determined The peritoneal clearance of each GC during one session of dialysate exchange.The value of peritoneal clearance of methyl guanidine (MG) was 4.56±1.02 ml/min (mean±SD), which was almost the same as that of urea-N and was higher than that of the other GCs.The values of peritoneal clearance of guanidinosuccinic acid (GSA), guanidinoacetic acid (GAA) and creatinine were 3.76±0.97, 3.72±1.18 and 3.53±0.90ml/min, respectively.In two patients who has experienced CAPD treatment for 22 months, there was marked decrease in the serum GSA level after a initiation of the treatment in spite of the absence of a change in serum GAA and MG levels.The decrease in the serum GSA level during the treatment showed a close correlation with the elevation of the hematocrit and the improvement in metabolic acidosis.The ratio of serum GSA to BUN (GSA/BUN) was 4.30×10^-3at the beginning of the treatment, which was compatible with that (5.24±3.21×10^-3) in patients with chronic renal failure under maintenance hemodialysis (MHD) therapy.After initiation of the treatment the ratio decreased to 2.11±0.98×10^-3, compatible with that (2.02±1.33×103) in patients with CRF under conservative therapy. These results indicate that in CAPD treatment GSA synthesis may be diminished through some mechanisms resulting in a decrease in the serum GSA level and the GSA/BUN ratio.An improvement in metabolic acidosis might be one of several factors contributing to the suppression of GSA production. In the contrast the serum GAA levels showed no change in the course of CAPD treatment.These results are not compatible with the finding in patients under MHD therapy, as we had observed the restoration of serum GAA to the normal level in the latter patients.Further observation of serum GAA levels might be needed in patients under CAPD treatment. There was no change in the serum MG level after initiation of the treatment in spite of a higher peritoneal clearance value.Serum MG concentration may not always indicate the whole body pool of MG, because MG is mainly distributed to the intracellular fluid compartment. In addition, the synthesis of MG from Cr might not be suppressed during the CAPD treatment, because transperitoneal removal of Cr was not effective because of its low peritoneal clearance.