Brain capillaries: a target for inorganic lead poisoning.

Like nutrients and waste products, toxic metals enter and leave the brain by passing through the endothelial cells of brain capillaries. In contrast to most systemic organs, the endothelial cells of the brain microvasculature are sealed together by tight junctions. The result is a blood-brain barrier produced by a continuous layer of endothelial cells. Since heavy metals most likely pass through these cells to enter the brain, it is not surprising that the metals may accumulate within and injure the capillary cells. This review will consider some of the features that distinguish endothelial cells in the brain from those in systemic organs. Special consideration will be given to processes shown in the Figure which may influence the transport and toxicity of inorganic lead.