Comparative study of effects of lead on the activity of erythrocyte pyrimidine 5′-nucleotidase and delta-aminolevulinate dehydratase in vivo and in vitro

The effect of lead on the activities of erythrocyte pyrimidine 5′-nucleotidase (Py5N) and delta-aminolevulinate dehydratase (ALA-D) was studied in the mice which were given ad libitum a drinking water containing lead of 10, 50 and 250 ppm, for 27 days. The erythrocyte Py5N activity was not decreased in all groups of lead-exposed mice. However, the erythrocyte ALA-D activity was markedly decreased in the groups exposed to 50 and 250 ppm lead. These data indicate that erythrocyte ALA-D is more sensitive than Py5N to lead in vivo. On the other hand, from the in vitro study, it was demonstrated that the human erythrocyte Py5N is moderately inhibited by zinc and tin, and markedly by mercury, cadmium, silver, copper, and lead, at 10⁻⁴ molar concentrations. In addition, it was observed that the erythrocyte Py5N is most remarkably inhibited by mercury while the ALA-D by lead, among metals tested.