Abstract

Millar, J. A., Thompson, G. G., Goldberg, A., Barry, P. S. I., and Lowe, E. H. (1972).Brit. J. industr. Med.,29, 317-320. δ-Aminolevulinic acid dehydrase activity in the blood of men working with lead alkyls. The activity of erythrocyte ALA¹-dehydrase is inhibited in vivo at blood lead (Pb²⁺) levels within the upper range of normal (20-40 μg/100 ml) and in vitro at lead concentrations greater than 10^-7 M. In view of the high sensitivity of the enzyme to Pb²⁺, the levels of enzyme activity in the blood of men occupationally exposed to lead alkyls, particularly tetraethyllead, were measured. It was found that the enzyme activity in an exposed group of men was significantly less (P<0·001) than in a control group, the respective mean values being 220 and 677 units of enzyme activity.

Tetraethyllead is metabolized in the body via triethyllead and diethyllead ions. As the latter compound possesses properties similar to Pb²⁺, it was synthesized in the laboratory and its effect on ALA-dehydrase was studied. Diethyllead ion was found to inhibit ALA-dehydrase activity at concentrations greater than 5 x 10^-5 M, although the degree of inhibition was less than that obtained with Pb²⁺. These results suggest that exposure to tetraethyllead can cause a decrease in erythrocyte ALA-dehydrase activity.