Effect of lead exposure on some biological indices related to porphyrin metabolism and the activity of erythrocyte pyrimidine 5'-nucleotidase in the mice.

The urinary excretion of delta-aminolevulinic acid (ALA) and coproporphyrin (CP) isomers (I and III) was investigated in mice exposed to lead in drinking water (200 and 500 ppm) for 14 or 30 days. Furthermore, the inhibition of pyrimidine 5'-nucleotidase (P5N) and delta-aminolevulinic acid dehydratase (ALAD) was studied in the same mice. In the lead-exposed mice, urinary excretion of ALA was significantly elevated (12-times control), while that of CP remained unchanged. This discrepancy on the urinary excretion may be of interest. The P5N activity in both erythrocytes and bone marrow cells was significantly inhibited by exposure to lead. However, the degree of inhibition was greater in the erythrocytes (45% inhibition) than in the bone marrow cells (25% inhibition). The inhibition of ALAD was much higher in erythrocytes (90% inhibition) than in liver (20-40% inhibition). The increase in erythrocyte protoporphyrin and the decrease in both hemoglobin and hematocrit were not observed in mice exposed to lead under the above conditions.