[First elements of comparison between blood-tissue barriers at cerebral, genital and urinary levels]

Fluorescence microscope observations of Trypan Blue distribution gives the demonstration of the blood-tissue barriers. It reveals the similitude between the barriers in choroid plexus, in testis, epididymis and bladder and the difference with the blood-brain barrier. Electron microscope investigations afford a statistical view of relations between structure and vascular permeability and stress the opposition reported above. Membrane specializations of each epithelium often bring forward those which are involved in the barrier. This function is principally assigned to thight junctions. The different morphological aspects encountered lead to the problem of dynamic variations in the configuration of the junctions.