Nicotinamide adenine dinucleotide synthetase activity in erythrocytes as a tool for the biological monitoring of lead exposure

Abstract

Objective: The objective of this study was to evaluate the usefulness of nicotinamide adenine dinucleotide synthetase (NADS) activity for the biological monitoring of lead exposure.

Methods: The subjects were 76 male lead workers and 13 normal volunteers (7 males and 6 females). NADS activity and blood lead concentration (Pb-B) was determined in each subject. Delta-aminolevulinic acid dehydratase (ALAD) activity was determined in 58 lead workers out of 76 subjects.

Results: NADS activity in the lead workers ranged from 0.08 to 1.1 μmol/h per g of hemoglobin (gHb) and decreased linearly (r = − 0.867) as Pb-B increased up to 81.6 μg/dl. The pattern of depressed activity of NADS was different from that of ALAD activity, which decreased rapidly and reached a plateau at the Pb-B level between 40 and 60 μg/dl. The Pb-B levels inducing 50% inhibition of the enzyme activities were calculated to be 43 μg/dl and 20 μg/dl for NADS and ALAD, respectively. At the Pb-B level of 40 μg/dl, NADS activity showed high validity (1.77) with predictivity of 0.92 at the cut-off level of 0.4 μmol/h per gHb, which were higher than those of ALAD activity.

Conclusions: These results show an apparent dose-effect relationship of NADS activity versus Pb-B. NADS activity can be used for the biological monitoring of lead exposure.