INTRA-CEREBRAL ARTERIOLAR PERMEABILITY TO LANTHANUM

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 107  (3) , 336-341
Abstract
La, an electron-dense tracer, has been used extensively in the study of the structure of cell junctions. To determine whether the interendothelial junctions of normal intracerebral arterioles allow passage of La and to document the alterations occurring in these structures in acute hypertension, perfusion of La for 12-40 min in control animals [rats] was peformed. This resulted in a passage of tracer into arteriolar walls and into the extracellular compartment of the surrounding brain. The 2 principal mechanisms associated with tracer extravasation into the brain were diffuse passage through endothelial cytoplasm and through interendothelial spaces bypassing tight junctions. The latter finding has not been previously reported in normal cerebral arterioles and suggests that the tight junctions of these vessels are different from those of capillaries and consist of a meshwork of closely arranged maculae occludentes, rather than complete circumferential occluding bands as was previously believed. Hypertensive animals showed accelerated passage of La, it being demonstrable not only in arteriolar walls but in capillary and venular walls as well as the surrounding neuropil after only 5 min of circulation. Passage of tracer through vessel walls occurred by the same routes as in controls. Increased numbers of pinocytotic vesicles were observed in the endothelium, confirming previous studies that increased vesicular transport ocurs in cerebral arteriolar endothelium in acute hypertension.