Alterations of adrenoceptors in the nasal mucosa of allergic patients in comparison with nonallergic individuals

Abstract

Nasal hyperreactivity in nasal allergy may be due to changes of the characteristics in adrenergic receptors. Radioligand receptor-binding studies with the antagonists, ³H-prazosin (α₁-adrenoceptor), ³H-rauwolscine (α₂-adrenoceptor), and ¹²⁵I-(−)-Cyanopindolol (β-adrenoceptor) were performed in homogenates of nasal mucosa of allergic and nonallergic (NA) patients to investigate this hypothesis. The heterogeneous NA group was subdivided into control individuals and patients with chronic sinusitis and vasomotor rhinitis. No significant differences in affinities or densities of α₁- and α₂-adrenoceptors could be demonstrated in allergic patients in comparison with NA and control individuals. The β-adrenoceptor density was significantly reduced in allergic patients in comparison with that of control individuals. Neither changes in agonist binding or in the effect of Gpp(NH)p on the agonist binding to β-adrenoceptors could be observed in allergic patients. The subtype selective antagonist, LK_203-030, demonstrated the presence of a homogeneous population of β₂-adrenoceptors in human nasal mucosa of both NA and allergic patients. In vitro, autoradiography demonstrated specific ¹²⁵I-(−)-Cyanopindolol labeling of the epithelium in NA and allergic patients. In conclusion, no changes in characteristics of α₁- or α₂-adrenoceptors in the nasal mucosa could be demonstrated in nasal allergy. However, a decreased number of β-adrenoceptors may reflect a β-adrenergic abnormality in nasal allergy.