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 has not been studied previously and the effect of angiotensin II (AII) on bronchomotor tone in vivo is unknown.


METHODS
Plasma levels of renin and AII levels were measured in 20 patients with acute severe asthma, nine with mild asthma, 10 with severe chronic asthma, and 16 normal volunteers. The effect of AII, given as an intravenous infusion, on bronchomotor tone was also investigated in eight mild asthmatic patients.


RESULTS
In acute severe asthma plasma levels of renin [median (interquartile range)] were elevated on days 1, 2, and 5 after admission [48.7 (24-79), 44.2 (15-75), and 45.5 (21-70) microU/ml, respectively]. Plasma 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 FEV1 of 0.34 (0.13) litres 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 acute asthma and AII causes bronchoconstriction in vivo in man. These observations suggest that in some patients AII may contribute to bronchoconstriction during acute severe asthma.
Millar
E A
EA
Department of Respiratory Medicine, Western Infirmary, Glasgow.
Angus
R M
RM
Hulks
G
G
Morton
J J
JJ
Connell
J M
JM
Thomson
N C
NC
D000208:Acute Disease; D000328:Adult; D000804:Angiotensin II / Q000097:blood / Q000494:pharmacology*; D001249:Asthma / Q000097:blood / Q000503:physiopathology* / Q000652:urine; D001794:Blood Pressure / Q000187:drug effects; D016084:Bronchoconstriction / Q000187:drug effects*; D002908:Chronic Disease; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000502:physiology*; D012964:Sodium / Q000652:urine
D000804:Angiotensin II; D012964:Sodium; D012083:Renin; D010100:Oxygen