In vivo interaction of lead with aminolevulinic acid dehydratase and induction of a thermolabile factor: an experimental model.

Aminolevulinic acid dehydratase (ALA-D) activity of male albino Wistar rats was used as an experimental model for a study on the interaction of lead with biological systems. Lead at 1 mg/kg was administered i.p. and the rats were killed immediately, and at 30 min, 1, 2, 3, and 4 h after treatment. It was shown that lead (Pb) interacted directly with the enzyme molecule immediately after treatment, first on the active site of zinc (Zn) and then on the thiolic groups. Induction of the so-called thermolabile factor (TF) seemed to occur later, i.e., it may only be shown from the 2nd-3rd h after treatment. The long-term persistence of lead-induced TF in the acute phase of intoxication may be the key to the interpretation of some chronic toxic effects.