Rm. Angus et al., EFFECT OF INHALED ATRIAL-NATRIURETIC-PEPTIDE ON METHACHOLINE-INDUCED BRONCHOCONSTRICTION IN ASTHMA, Clinical and experimental allergy, 24(8), 1994, pp. 784-788
We have previously demonstrated that intravenous and inhaled atrial na
triuretic peptide (ANP) significantly inhibits histamine induced bronc
hoconstriction in asthmatic patients. The current study was designed t
o determine whether inhaled ANP was also able to inhibit the effects o
f methacholine. Eight atopic asthmatic patients (five women) were stud
ied: mean (SD) age 38.2 (8.3) years flow expiratory volume per second
(FEV(1)) 2.97 (0.60) litres, equivalent to 92 (13) % of the predicted.
Each had demonstrated at least mild bronchial hyperreactivity to inha
led methacholine at screening (geometric mean PC20 1.02mg/ml; range 0.
11-6.54mg/ml). Patients attended for 3 study days and after baseline s
pirometry received 3.5ml saline (placebo), 0.1mg ANP or 1 mg ANP (ANP
dissolved in 3.5ml saline) in a randomized, double-blind manner via a
Miter aerosol conservation device. Aerosolization took approximately 9
min and FEV(1) was repeated at 0.5, 1.5 and 3 min after completion. I
mmediately thereafter each patient received a 2min inhalation of metha
choline at a dose individually calculated to give a 25% fall in FEV(1)
(as extrapolated at their initial screening visit) and the FEV(1) was
followed over the next 20 min. Mean (SEM)% FEV(1) did not change sign
ificantly after ANP being -4.3 (1.7), -3.2 (2.7) and -2.4 (1.2) after
placebo, 0.1 mg ANP and 1 mg ANP respectively. The mean (SEM) maximum
fall in FEV(1) after methacholine was as follows: placebo 26.9 (5.7)%,
0.1 mg ANP 18.2 (4.3)% and 1.0 mg 11.2 (2.7)% (P < 0.05 placebo vs 1
mg ANP). These results demonstrate that ANP offers significant protect
ion against methacholine induced bronchoconstriction in asthmatic pati
ents.