Adrenergic airway vascular smooth muscle responsiveness in healthy and asthmatic subjects

The purpose of the present study was to determine the responsiveness of air way vascular smooth muscle (AVSM) as assessed by airway mucosal blood flow ((Q) over dotaw) to inhaled methoxamine (alpha (1)-agonist; 0.6-2.3 mg) and albuterol (beta (2)-agonist; 0.2-1.2 mg) in healthy [n = 11; forced expira tory volume in 1 s, 92 +/- 4 (SE) % of predicted] and asthmatic (n = 11, me an forced expiratory volume in 1 s, 81 +/- 5%) adults. Mean baseline values for (Q) over dotaw were 43.8 +/- 0.7 and 54.3 +/- 0.8 mul.min(-1).ml(-1) o f anatomic dead space in healthy and asthmatic subjects, respectively (P < 0.05). After methoxamine inhalation, the maximal mean change in (Q) over do taw was -13.5 +/- 1.0 <mu>l.min(-1).ml(-1) in asthmatic and -7.1 +/- 2.1 mu l.min(-1).ml(-1) in healthy subjects (P < 0.05). After albuterol, the mean maximal change in (Q) over dotaw was 3.0 +/- 0.8 <mu>l.min(-1).ml(-1) in as thmatic and 14.0 +/- 1.1 mul.min(-1).ml(-1) in healthy subjects (P < 0.05). These results demonstrate that the contractile response of AVSM to <alpha> (1)-adrenoceptor activation is enhanced and the dilator response of AVSM to beta (2)-adrenoceptor activation is blunted in asthmatic subjects.