Histamine H1 Receptors and Affinity Analyses in Human Nasal Mucosa in Cases of Nasal Allergy

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Abstract
An increased number (density) or sensitivity (affinity) of histamine H1 receptors could cause an increase of allergic symptoms. Using the specific H1 receptor blocker 3H-mepyramine, we have demonstrated for the first time an H1 receptor number (Bmax) and a binding affinity (Kd) in guinea pig and human nasal mucosa. H1 antihistamines inhibited 3H-mepyramine binding in nasal mucosa at low concentrations, while H2 antihistamines inhibited at extremely high concentrations, indicating that 3H-mepyramine binding sites represent H1 receptors in nasal mucosa. Bmax and Kd values were not significantly different among the nonallergic sinusitis, vasomotor rhinitis, or the nasal allergy group, suggesting that H1 receptors do not change quantitatively and qualitatively in allergic nasal mucosa. There was no significant correlation between H1 receptor number and clinical data (IgE, peripheral eosinophils, RAST). These data suggest that H1 receptor number and affinity are not main etiological and pathophysiological factors in nasal allergy.