HEME-BIOSYNTHESIS IN UREMIC PATIENTS ON CAPD OR HEMODIALYSIS

We have analyzed some parameters of porphyrin metabolism in 60 patient s with end-stage renal failure, 20 of them on CAPD and the remaining o n HD. In comparison with 56 control subjects, both groups of patients showed the three following findings: low erythrocyte aminolevulinate d ehydrase activity, inhibition ability for the activity of this enzyme when their plasma was incubated in vitro with normal erythrocytes, and increased plasma porphyrin levels. Like anemia, these abnormalities w ere more remarkable in patients on HD who also exhibited increased ery throcyte protoporphyrin levels and compensatory porphobilinogen deamin ase activities. Mean weekly porphyrin removal through dialysate was hi gher in CAPD (90.8 mug) than in HD patients (30.4 mug). Dialysate and plasma porphyrins were correlated in both circumstances (r = 0.714, P < 0.01 and r = 0.637, P < 0.05, respectively). The less pronounced por phyrin abnormalities found in CAPD patients with respect to HD patient s may be due to the more efficient capability of peritoneal dialysis f or removing from plasma protein-bound substances, as porphyrins and in hibitors of aminolevulinate dehydrase or other enzymes involved in ery thropoiesis. Since no close relationship was found between these abnor malities of porphyrin metabolism and hematocrit values, the anemia of uremia cannot be merely considered as a direct consequence of altered heme biosynthetic pathway.