Studies on the Underhydroxylated Basement Membrane Procollagen Synthesized by Rat Parietal Yolk Sacs in the Presence of α, α'-Dipydridyl

Rat embryo parietal yolk sacs synthesized and secreted underhydroxylated [14C]proline-labeled basement membrane procollagen when incubated in the presence of the iron chelator alpha,alpha'-dipyridyl and [14C]proline. Upon reduction and sodium dodecyl sulfate-agarose gel filtration, this procollagen eluted as a discrete peak of labeled material close to the position of the beta components of type I collagen. Secreted underhydroxylated procollagen contained interchain disulfide bonds and was completely degraded by a 6 hr treatment with alpha-chymotrypsin at 4 degrees C. Results from 4 hr incubations indicated that the distribution of 14C-procollagen between tissue and medium was unaffected by the presence of alpha,alpha'-dipyridyl, but analysis of results from pulse-label and chase experiments revealed that underhydroxylated procollagen was secreted at less than half the rate of control procollagen.