Lead poisoning and the blood-brain barrier.

Lead exposure may produce varying degrees of neuropsychiatric manifestations from discrete phenomena, quite often seen in children and as an occupational disease, to the rate fulminant lead encephalopathy. It was determined whether or not damage of the blood-brain barrier permeability in adult rats, as has been demonstrated in neonatal animals exposed to lead, could also play a role. Massive lead exposure did not induce any change in the transfer (facilitated diffusion) of phenylalanine any tyrosine measured by means of the indicator dilution technique. Ultrastructural examination, after application of horseradish peroxidase, did not reveal any pathological changes in the permeability to the tracer. It is concluded that in adult rats, in contrast to neonatal animals, the observed pathological signs clearly seen in the chronically exposed animals must be ascribed to a noxious influence of lead on the extravascular side of the blood-brain barrier.