Delta aminolevulinic acid dehydratase amounts in lead-exposed subjects: description of a method correlated with the immunoturbidimetric assay

The measurement of d-aminolevulinic acid dehydratase (ALA.D) activity is a good index of lead exposure. Recently, we proposed an immunotubidimetric assay which allows determination of the amount of the enzyme. This last test is particularly interesting for workers presenting high blood-lead levels. We then studied the effects of different agents (dithiothreitol, heat and zinc ions) in restoring the activity of lead-inhibited ALA.D. The individual or combined effects of these three agents showed an additive restoration of activity. The combination of zinc ions with heat and/or DTT gave the best activations, which correlated perfectly with ALA.D amounts. Consequently, the catalytic assay using zinc ions and DTT may be used in routine testing as an indirect measurement of ALA.D amount.