An autoradiographic study on the biosynthesis of the capillary basal lamina in the chick embryo telencephalon.

The elaboration of the basal lamina of telencephalic capillaries has been studied by autoradiography in chick embryos from day 16 to 19 of incubation. The cerebral vascular basal lamina is actively synthesized during the period of these stages of development. The animals were sacrificed 2, 15, 40 and 180 min after intravenous injection of 3H-proline. The hydroxylation of proline to hydroxyproline in the "secretory" cells permits their identification. Our observations suggest that endothelial cells, pericytes and perhaps glial cells participate in this elaboration. The various stages of the synthesis are performed sequentially in the ergastoplasm and then in the Golgi apparatus before the secretory material is released by exocytosis.