[Histochemical correlations of vascular permeability and enzyme activity in the choroid plexus in man]

The choroid plexuses are characterized by the absence of alcaline phosphatase activity as well as the absence of any vascular barrier for proteins as revealed by fluorescein tracer observation. This correlation is interpreted as supporting the hypothesis of enzymatic control, via alcaline phosphatase, of the blood-brain barrier. Adenosine mono and triphosphatase activity, on the contrary, is identical in choroid plexus vessels and in vessels where the blood-brain barrier phenomena may be demonstrated.