Some parameters of haem synthesis in dialysed and non-dialysed uraemic patients.

Some parameters of haem synthesis were estimated in 60 uraemic patients (30 non-dialysed, 30 dialysed) and in 30 matched controls. Serum delta-aminolaevulinic acid and erythrocyte coproporphyrin and protoprophyrin were found significantly higher in the non-dialysed uraemics than in the controls. Erythrocyte delta-aminolaevulinic acid dehydrase (ALA-D) activity was 498 +/- 174 mumol/h.l in the non-dialysed patients, 321 +/- 146 in the dialysed (just before haemodialysis) and 833 +/- 281 in the healthy controls, the differences between these groups all being statistically significant (p less than 0.001). After haemodialysis the enzymic activity in the dialysed group increased significantly (380 +/- 167, p less than 0.001), but remained lower than normal (p less than 0.001). A similar pattern - although with less statistical significance of the differences between groups - was observed concerning erythrocyte uroporphyrinogen I synthase activity. Incubation of normal erythrocytes with uraemic plasma resulted in a considerable decrease of their ALA-D activity (from 830 +/- 263 to 616 +/- 126) while incubation of uraemic erythrocytes with normal plasma increased their ALA-D (from 384 +/- 139 to 494 +/- 77). Addition of zinc in the haemolysate caused a similar induction of ALA-D in both controls and uraemics. The zinc-induced uraemic ALA-D practically reached normal levels. The mechanism of enzymic depression and the possible role of elevated delta-aminolaevulinic acid concentrations (to which depressed ALA-D activity considerably contributes) in the pathogenesis of the neurologic manifestations of uraemia, are discussed.