Subcellular localization of lead in synaptosomes.

The neurotoxicology of lead is reported to involve effects on cholinergic and monoaminergic pathways. However, no information is available on the site of action at which lead exerts neurotoxic effects. The technique of x-ray elemental analysis coupled scanning-transmission mode electron microscopy has been applied to study the in vitro interactions of lead with synaptosomes. To minimize possible translocation effects on elemental distribution, isolated synaptosomes were air dried on EM grids; no fixing or staining procedures were used. In such preparations, synaptosomes and intrasynaptosomal mitochondria were distinguishable. Lead was found only in mitochondria in association with Ca ad P. Thus, lead appears to enter isolated nerve terminals and to be sequestered in mitochondria.