Effects of popcorn butter flavorings, diacetyl and 2,3-pentanedione, on isolated airway preparations.
RATIONALE: "Popcorn workers' lung" is a life-threatening, fixed obstructive pulmonary disease caused by inhalation of butter flavoring vapor. Histological evidence from animals exposed by inhalation to the butter flavorings, diacetyl (2,3-butanedione), and a diacetyl substitute, 2,3-pentanedione (acetyl proprionyl), demonstrated vapor-concentration-dependent damage to epithelial cells. Because nothing is known about the effects of diacetyl and 2,3-pentanedione on airway smooth muscle (ASM), we investigated the pharmacological activity of these two flavorings on isolated airways. METHODS: In rat isolated, perfused tracheas, the contractile and relaxant effects of diacetyl and 2,3-pentanedione applied to the serosal and mucosal surfaces of intact and denuded contracted (MCh; 3x10-5 M) tracheas were evaluated. RESULTS: Concentrations of both agents greater than 3 mM resulted in ASM relaxation. Relaxation of the trachea by diacetyl and 2,3-pentanedione was not dependent upon the presence of the epithelium. CONCLUSIONS: Our findings indicate that both flavorings are similar in their effects as ASM relaxants.