Organ cultures of the embryonic rat parietal yolk sac: I. Morphologic and autoradiographic studies of the deposition of the collagen and noncollagen glycoprotein components of basement membrane

Abstract

The synthesis, deposition, and turnover of [ 3H]proline- and [ 3H]glucosamine-labeled basement membrane components have been studied in a system using organ cultures of embryonic rat parietal yolk sac tissues on a nutrient agar substrate. The morphologic and autoradiographic studies described in this report were correlated with the biochemical studies described in the companion paper (Minor et al., Develop. Biol. 48, 1976). These studies showed that: (1) basement membrane (BM) was the only extracellular matrix synthesized in the cultures, (2) 10- to 30- μm thick layers of new BM were deposited during a 6-day culture period, (3) it was only the parietal endodermal cells that synthesized BM, (4) new BM was deposited only on the surface of existing BM, which was in contact with endodermal cells, (5) the amounts of new BM that accumulated were increased by a twice daily feeding schedule and decreased by the presence of trophoblast, (6) there was a notable difference in the redistribution of labeled components during a 6-day chase, and (7) [ 3H]glucosamine tended to localize in the Golgi complex, whereas [ 3H]proline was distributed throughout the cytoplasm of the endodermal cells.