Organ cultures of the embryonic rat parietal yolk sac: II. Synthesis, accumulation, and turnover of collagen and noncollagen basement membrane glycoproteins

Abstract

Synthesis, accumulation, and turnover of basement membrane components have been studied in organ cultures of 13.5- and 14.5-day embryonic rat parietal yolk sac tissues on a nutrient agar substrate. The biochemical studies described in this report were correlated with morphologic and autoradiographic studies described in the companion paper (Minor et al., Develop. Biol. 48, 1976). These studies showed that basement membrane is the only extracellular matrix synthesized, it is only synthesized by the parietal endodermal cells, and its synthesis is maintained for at least 6 days. In these cultures, synthesis and degradation of collagen and noncollagen proteins varied independently in response to environmental changes, such as the frequency of feeding or presence of trophoblast. The turnover of basement membrane collagen was much slower than that of the noncollagen proteins and this difference in the rate of turnover of the components had a major role in determining the composition of the newly synthesized basement membrane.