In vitro effect of lead in blood on the determination of delta-aminolevulinic acid dehydrase

Whole blood, as withdrawn, from lead-exposed dogs was added in varying proportions, to whole blood, as withdrawn, from normal (non-exposed) dogs. The resultant red cell ALADP activities and lead concentrations of the mixtures were then determined. It was found that the resultant ALAD activities could be predicted on the basis of simple dilution of the blood with normal ALAD activity by the blood with severely reduced ALAD activity. The observed values for ALAD of the mixtures related to resultant lead concentration according to the equation: Y = a+ bx, rather than to the equation log y = a+ bx as reportedly observed for samples of blood from lead-exposed humans, and from lead-fed dogs. There was no evidence that the ALAD activity contributed by the portion of normal blood in the mixture was affected by the lead contributed by the blood from the lead exposed dog. This is considered as evidence that the reduction in red cell ALAD activity observed in lead-exposed dogs is not an in vitro artifact inherent in the method used to determined ALAD activity...