241 zyxwvutsr Clinica Chimica Acfa, 104 (1980) 241- 244 0 Elsevier/North-Holland Biomedical Press zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPON SHORT COMMUNICATION CCA 1347 DETERMINATION OF ERYTHROCYTE UROPORPHYRINOGEN I SYNTHETASE ACTIVITY IN CHRONIC RENAL FAILURE A. ANDRIOLO, A.J. MOCELIN *, S.R. STELLA, H. AJZEN and O.L. RAMOS Nephrology Division, Escola Paul&a de Medicina, So Paul0 (Bra&) (Received June 29th, 1979) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCB Summary To obtain some information on porphyrin metabolism in uraemic patients, the activity of erythrocyte uroporphyrinogen I synthetase was measured in patients with chronic renal failure. The results indicate a decreased enzymatic activity which is not due to urea interference, in the hemolysates of these patients. Introduction Little is known of porphyrin metabolism in uraemic patients, despite evidence showing that medium-sized molecules (300 to 2000 molecular weight) can influence important steps in hemoglobin synthesis. We have studied some of these steps in patients with chronic renal failure of different etiologies zyxwvuts [W. Uroporphyrinogen I synthetase, URO-S (EC 4.3.1.8) catalyzes the conver- sion of porphobilinogen (PBG) to urobilinogen I. The measurement of URO-S activity in red blood cell hemolysates is useful in the diagnosis of acute inter- mittent porphyria [ 3,4,5], but it also provides information about the status of porphyrin synthesis in other conditions. In this paper we present our results concerning URO-S activity in erythro- cytes of uraemic patients. Material and methods The determination of erythrocyte URO-S activity was carried out according to Mandel [6 1. Normal values were obtained from 11 non-uraemic healthy zyxwvuts * To whom correspondence should be addressed.