Localization of newly synthesized protein precursors of basement membrane in the embryonic central nervous system as revealed by radioautography.

Using light- and electron microscope radioautography, the dynamics of newly synthesized protein precursors taking part in elaboration of brain basement membrane have been examined. The data presented give evidence that all cell types (endothelial, pericytal, and astroglial cells) surrounding the brain basement membrane contribute to its composition. A quantitative uptake analysis of 3H-proline indicates a progressive decline in the amount of labeled precursor in the examined cell types with a corresponding increase in deposition of the label at the presumptive basement membrane. The endothelial cells plays the main role in the membrane elaboration followed by pericyte and astrocyte which participate at lesser but equal degree in this synthesis.