Impairment of the β-Adrenergic System of Peripheral Blood Leukocytes in Atopic Patients with Seasonal Allergic...

Compared to 7 healthy women, an altered β2-adrenoceptor/cyclic adenosine monophosphate (cAMP) system has been observed in a combined study on both expression and function of β2-adrenoceptors on peripheral blood leukocytes (PBL) of 7 atopic women suffering from acute seasonal rhinoconjunctivitis. A reduced affinity of the β-adrenergic radioligand 125Icyanopindolol to its binding site (equilibrium dissociation constant Kd 6.4 ± 1.0 vs. 3.4 ± 0.6 pmol/l in controls; p <0.05) a reduced sensitivity of the intracellular cAMP formation to isoprenaline (concentration necessary to achieve half-maximal effectiveness EC501,088.6 ± 669.0 vs. 71.0 ± 51.0 nmol/l in controls; p <0.01), and a reduced intracellular cAMP increase in response to isoprenaline (Emax as a percentage of the basal cAMP content E₀ 117 ± 3 vs. 145 ± 8% E₀ in controls; p <0.01) point to a subsensitivity of β2-adrenoceptors. A reduced E₀ (4.9 ± 0.8 vs. 8.4 ± 1.3 pmol/l06 cells in controls; p <0.05) suggests an increased activity of the cAMP-degrading enzyme phosphodiesterase. A reduced sympathetic tone in atopy was further confirmed by lower cAMP plasma concentrations (25.7 ± 1.2 vs. 31.3 ± 1.6 nmol/l in controls; p <0.05). The results indicate that more than just one mechanism are involved in the impairment of the PBL β2-adrenoceptor/ cAMP system in atopy.