Generation of prostaglandin E-like material by the guinea-pig trachea contracted by histamine

Challenges of the superfused (1 ml min-1) trachea with histamine (100-200 mug) result in the release of prostaglandin E-like material (3-25 ng in terms of prostaglandin E2) but no prostaglandin F-like activity has been detected in the superfusate. This release is blocked by indomethacin (1mug ml-1) and then the contractile action of histamine is enhanced. It is concluded that the release of a prostaglandin E-like material by histamine from tracheal smooth muscles is a self-defensive mechanism protecting against the strong constriction of airways. The maximal relaxation of trachea by isoprenaline (50-500 mug) is not accompanied by the release of a prostaglandin-like material.