ACTIVITY OF THE RENIN-ANGIOTENSIN SYSTEM IN ACUTE SEVERE ASTHMA AND THE EFFECT OF ANGIOTENSIN-II ON LUNG-FUNCTION

Background - The activity of the renin-angiotensin system in asthma ha s not been studied previously and the effect of angiotensin II (AII) o n bronchomotor tone in vivo is unknown. Methods - Plasma levels of ren in and AII levels were measured in 20 patients with acute severe asthm a, nine with mild asthma, 10 with severe chronic asthma, and 16 normal volunteers. The effect of AII, given as an intravenous infusion, on b ronchomotor tone was also investigated in eight mild asthmatic patient s.Results - In acute severe asthma plasma levels of renin [median (int erquartile range)] were elevated on days 1, 2, and 5 after admission [ 48.7 (24-79), 44.2 (15-75), and 45.5 (21-70) mu U/ml, respectively]. P lasma AII levels were significantly elevated at day 5 [56 (12-109) pg/ ml]. In the second study a bronchoconstrictor response to intravenous AII was seen with a mean (SE) maximal fall in FEV(1) of 0.34 (0.13) li tres or 12.4 (3.3)% from baseline following the high dose infusion of AII (8 ng/kg/min) with a corresponding plasma AII concentration of 121 .3 pg/ml. Conclusions - The renin-angiotensin system is activated in a cute asthma and AII causes bronchoconstriction in vivo in man. These o bservations suggest that in some patients AII may contribute to bronch oconstriction asthma.