Endogenous inhibitor of prostaglandin biosynthesis in inflammation.

Rat serum exhibits a concentration-related inhibition of PG biosynthesis by rat peritoneal leucocytes phagocytosing killed bacteria. The serum inhibitory potency is increased by inducing carrageenan foot oedema in animals whereas it is not altered by dextran oedema. The increase of the inhibitory activity of serum from carrageenan-treated rats develops in a time-dependent way reaching its maximum at 24 h. Since the increased inhibitory activity does not occur following indomethacin administration we suggest that PG formation at the inflammatory site may stimulate the ability of serum to inhibit PG biosynthesis.