Connective tissue activation. VII. Evidence supporting a role for prostaglandins and cyclic nucleotides

Prostaglandins added to synovial cultures stimulated hyaluronic acid (HA) synthesis and glycolysis. The order of potency of the prostaglandins was: PGE1 greater than PGE2 greater than PGF2alpha greater than PGF1alpha, PGE1 and PGE2, 1.0 mug per milliliter, stimulated synovial cells, whereas F-series prostaglandins required 5 mug per milliliter for stimulation. Connective tissue-activating peptide (CTAP) activation of synovial cells was markedly potentiated by all four prostaglandins, and by PGE1 in concentrations as low as 0.01 mug per milliliter. Exogenous prostaglandins caused a prompt and marked increment in synovial cell cyclic-AMP, while CTAP caused a delayed peak of cyclic-AMP of lesser magnitude. Treatment of synovial cultures with cortisol (1.0 mug per milliliter), cycloheximide (10 mug per milliliter), or indomethacin (15.0 mug per milliliter) failed to block stimulation by PGE1, 7-OXA-13-Prostynoic acid, a prostaglandin antagonist, substantially inhibited the action of PGE1 and suppressed the effect of CTAP on synovial cells. It is possible that both exogenous and endogenous (synovial prostaglandins are involved in the connective tissue activation sequence.