The dual action of meclofenamate on the contractile response to PGF2 alpha in the guinea-pig trachea.

Indomethacin and meclofenamate (1 mug/ml) enhance contractile action of PGF2 alpha (5-20 mug) in guinea-pig tracheas superfused with Tyrode solution (5 ml/min). Unlike indomethacin, meclofenamate at a concentration of 10 mug/ml antagonizes contractions of guinea-pig tracheas produced by PGF2 alpha (5-20 mug), while the contractile action of histamine (0-5-2-0 mug) is enhanced. It is concluded that low concentrations of meclofenamate (1 mug/ml) inhibit prostaglandin biosynthesis in tracheal smooth muscles and therefore contractile action of exogenous PGF2 alpha is enhanced, while meclofenamate at a high concentration (10 mug/ml) blocks the receptor sites for PGF2 alpha.