Abnormal beta-adrenergic responsiveness in allergic subjects. II. The role of selective beta 2-adrenergic hyporeactivity.

Isoproterenol increases systolic blood pressure by increasing cardiac output through beta 1-adrenergic stimulation and lowers diastolic pressure by reducing peripheral resistance, which is a beta 2-adrenergic response. It was therefore possible to compare beta 1 and beta 2 responsiveness of allergic subjects to determine whether asthmatics behaved differently than did rhinitis patients or even "preallergic" subjects, who have positive skin tests in the absence of symptoms. All the allergic subjects required significantly more isoproterenol to increase their pulse pressure 22 mm Hg or greater as compared with normal subjects. Analysis of the beta 1 and beta 2 components of the pulse pressure change revealed normal beta 1 responses (systolic increase) and abnormal beta 2 responses (diastolic decrease) in all allergic groups. Moreover, even at the point where the pulse pressure was driven to increase by 22 mm Hg or more, the allergic subjects had a reduced diastolic (beta 2) component. These studies demonstrate beta-adrenergic abnormalities in allergic subjects who were well controlled for concomitant drug administration, thereby extending and confirming the results of many earlier studies. In addition, this study extends the selective beta 2-adrenergic defect to all allergic subjects, not just asthmatics, as was suspected earlier.