NORMAL RESPONSIVENESS OF SUPERFICIAL HAND VEINS TO ALPHA-ADRENERGIC AND BETA-ADRENERGIC STIMULI IN ALLERGIC-ASTHMA - EFFECTS OF TERBUTALINE AND PREDNISOLONE ON BETA-ADRENERGIC RESPONSIVENESS

Impaired function of the adrenergic-receptor system has been postulated to contribute to the pathogenesis of bronchial asthma. Using the dorsal hand-vein compliance technique, we compared the changes in diameter of superficial hand veins in response to phenylephrine, an α-adrenoceptor agonist, and to isoproterenol, a β-adrenoceptor agonist, in 14 untreated patients with allergic asthma and in 16 nonatopic control subjects. There were no significant differences in the median effective dose of phenylephrine that produced 50% of maximal venoconstriction (ED50) or in the maximal response (Emax) between the two groups. Bronchial hyperreactivity (assessed by methacholine-challenge tests) in the patients with asthma was uncorrelated with the ED50 or Emax of isoproterenol. These results demonstrate no evidence for a generalized change in α-or β-adrenergic responsiveness on smooth muscle cells in asthma. Hand-vein responsiveness to isoproterenol was unchanged after treatment for 7 days with oral terbutaline (5 mg three times per day). Thus unlike leukocytes, smooth muscle appears not readily susceptible to β-adrenoceptor densensitization in vivo. Local infusions of prednisolone or dexamethasone during 2 hours and systemic administration of dexamethasone (24 hours) caused a significant fall in the Emax for isoproterenol. The mechanism of attenuation of β-adrenoceptor responsiveness by corticosteroids remains to be determined. © 1990 Mosby-Year Book, Inc.