Modulation of prostaglandin E2 synthesis in rabbit synoviocytes

Prostaglandin E2 (PGE2) production by rabbit synoviocytes was markedly stimulated by hydroxyapatite only after a 60-minute delay. Release of 3H-arachidonic acid (C20:4) and 3H-PGE2 from cells with phospholipids that were prelabeled with 3H-C20:4 did not occur in parallel. At 240 minutes, phospholipase activity in sonicated cell suspensions had increased only 38%, while cyclooxygenase activity had doubled (109%). This doubling, as well as the production of synoviocyte PGE2, was prevented by inhibiting the synthesis of protein. Cyclooxygenase is an inducible enzyme, and as such, it is a rate-controlling step in PGE2 production.