The cyclic AMP system in sensitized and desensitized guinea-pig tracheal smooth muscle.

Egg albumin decreased the cyclic AMP content and the protein kinase ratio of sensitized guinea-pig tracheal smooth muscle. The effect preceded the contraction of the tracheal preparation. Antigen challenge increased cyclic AMP phosphodiesterase activity without changing the Km value. In tracheal preparations of desensitized guinea-pigs, the mechanical and metabolic effects of egg albumin were markedly reduced. These results suggest that the effects on the cyclic AMP system in response to immunological challenge might represent an important mechanism modulating the contractile response of guinea-pig tracheal smooth muscle.