Relationship between activation of delta-aminolevulinic acid dehydratase by heating and blood lead level

Both blood lead and erythrocyte delta-aminolevulinic acid dehydratase (ALA-D) activity were determined for workers with and without an occupational lead exposure. In workers occupationally exposed to lead, it was demonstrated that the erythrocyte ALA-D is markedly activated by heating the hemolysate at 60 degrees C for 5 min and there is a good positive correlation between the ratio of heated to nonheated ALA-D activity and the blood lead level (r=0.799). In addition, by heating the hemolsyate, the ALA-D activity of the lead-exposed workers appears to be returned into the normal range regardless of the extent of lead absorption. However, in normal workers without the occupational lead exposure, no significant correlation was found between the ratio of heated to nonheated ALA-D activity and the blood head level, although the normal ALA-D also can be slightly activated by heating the hemolysate at 60 degrees C for 5 min.