The rat anococcygeus muscle is a convenient bioassay organ for the airway epithelium-derived relaxant factor

Abstract

The response to epithelium-derived relaxant factor (EpDRF) released from guinea-pig trachea by acetylcholine was studied in the precontracted rat anococcygeus muscle in a coaxial bioassay system. Acetylcholine caused no relaxation of rat anococcygeus muscle which was precontracted with phenylephrine. When the same muscle was placed into a guinea-pig trachea with intact epithelium, acetylcholine produced a slowly developing relaxation which was potentiated by neostigmine and antagonized by atropine but was not altered by indomethacin, propranolol, hydroquinone nor methylene blue. The rat anococcygeus muscle was not relaxed by acetylcholine when it was placed in an epithelium-free trachea. The results indicate that acetylcholine releases EpDRF from guinea-pig trachea and that rat anococcygeus muscle is a convenient organ for the bioassay of EpDRF.