INVESTIGATIONS ON THE RENIN-ANGIOTENSIN SYSTEM IN ACUTE SEVERE ASTHMA

The renin-angiotensin system is activated in acute severe asthma. The precise mechanism of activation is at present unknown, but may involve , beta(2)-agonists, catecholamines or proteases released in airway inf lammation, This study aims to identify potential factors involved in t he activation of the renin-angiotensin system in acute asthma, Forty a sthmatics with severe exacerbations of asthma, assessed by measurement of peak expiratory flow rate (mean (SD) 35 (18)% predicted), oxygen s aturation (94 (4)%) and pulse rate (108 (16) beats.min(-1)) were recru ited, Nineteen (48%) asthmatics had elevated plasma angiotensin II lev els (median (interquartile range) 10.9 (4.3-23.5) pg.mL(-1) (normal ra nge 3-12 pg.mL(-1))) and 10 (25%) had elevated plasma renin concentrat ion (22.0 (10.0-50.0) mu U.mL(-1) (normal range 9-50 mu U.mL(-1))). Pl asma renin and angiotensin II correlated strongly, implying renin-depe ndent angiotensin II formation, No correlation was found between plasm a salbutamol, adrenaline, nor-adrenaline, endothelin-l, histamine, eos inophilic cationic protein, serum angio-tensin-converting enzyme (ACE) activity, total immunoglobulin E (IgE), urea and electrolytes, indica tors of the severity of the attack, atopic status, blood pressure and renin or angiotensin II levels. We conclude that although a subpopulat ion of asthmatics appear to have raised renin and angiotensin II durin g attacks of acute, severe asthma, the mechanism of activation of the renin-angiotensin system remains unclear.