Immunological and enzymatic studies of erythrocytic delta-aminolevulinate dehydratase. Comparison of results obtained in normal and lead-exposed subjects.

The delta-aminolevulinate dehydratase (ALA.D) quantitative assay on a centrifugal fast analyser showed that subjects whose blood-lead level varies between 30 and 75 micrograms/100 ml (1.5 to 3.75 microM/l) react to blood intoxication by synthesizing de novo an amount of enzyme correlating to blood-lead levels. At higher concentrations, the reactional synthesis occurs very rarely. These results suggest that enzyme is constitutive, but also inductible as soon as its substrate accumulates; this last ability may disappear at high blood-lead levels: a hypothesis is proposed thereafter.