Biphasic effects of prostaglandin E2 on bone formation in cultured fetal rat calvariae: interaction with cortisol.

TLDR: Results indicate that PGE2 can regulate bone collagen synthesis at a pretranslational site and show that it was not dependent on cell replication.

Abstract: Previous studies have shown that prostaglandin E2 (PGE2) has both inhibitory and stimulatory effects on the incorporation of proline into collagenase-digestible protein (CDP) in cultured fetal rat calvaria. The present studies were undertaken to analyze further these biphasic effects of PGE2. PGE2 increased [3H]thymidine incorporation at 24 h, and this effect was enhanced in the presence of cortisol (10-8 and 10-7M). An inhibitory effect on CDP labeling was observed at 96 h with PGE2 (10-6 M) in the absence or presence of indomethacin (10-6 M), but not in the presence of cortisol (10-8 or 10-7 M). When the central osteoblast-rich bone and periosteum were analyzed separately, the inhibitory effect of PGE2, with or without indomethacin, was confined to the central bone. Addition of aphidicolin (30 μM), an inhibitor of cell replication, did not prevent the inhibitory effect of PGE2 on CDP labeling. Analysis of labeled collagen by polyacrylamide gel electrophoresis showed a decrease in labeling of type I coll...