Effects of inhalation of N-formyl-methionyl-leucyl-phenylalanine in the well elderly and in patients with chronic bronchitis.

BACKGROUND Inhalation of the bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) produces bronchoconstriction in normal subjects. FMLP thus has a putative role as a mediator of bronchoconstriction associated with bacterial bronchial infection. METHODS The effects of FMLP inhalation were examined in ten subjects with a history of chronic bronchitis and ten age matched control subjects. Each subject inhaled FMLP doses from 0.025 to 0.8 mumol to determine the provocative dose of FMLP causing a 20% fall in FEV1(PD20FMLP). FEV1 was recorded every five minutes after the final FMLP inhalation until it had returned to 95% of baseline FEV1 or 60 minutes had elapsed. The time to return to 95% baseline FEV1 was recorded or extrapolated from the recovery curve as an index of rapidity of recovery. Total and differential white cell counts were performed on each subject at baseline and five and 15 minutes after the final FMLP inhalation. RESULTS The geometric mean PD20 FMLP in the patients with chronic bronchitis was 0.06 mumol (95% confidence interval 0.015-0.26), which was significantly lower than that in the control subjects (0.21 mumol (0.02-1.9)). PD20 FMLP in the patients with chronic bronchitis but not age matched controls (p = 0.35) was lower than that found previously in young normal subjects (0.35 mumol (0.07-1.8). The return to 95% baseline FEV1 occurred after 86(10) minutes in subjects with chronic bronchitis and in 81(23) minutes in their age matched controls, in both cases being much slower than that seen in young subjects (29(9) minutes). CONCLUSION Patients with chronic bronchitis may be especially susceptible to formyl peptides elaborated by bacteria during bacterial bronchial infection.