β2-adrenergic receptor ( β AR) density on peripheral blood lymphocytes has been used as an index to reflect the β AR state of the body. Lymphocytes β ARs are unequally distributed among lymphocyte subpopulations, with the highest density on CD8 + cells and the lowest on CD4 + cells. Thus, the measurement of peripheral blood lymphocyte β AR density could vary with changes in CD4 + and CD8 + cell concentrations. We examined the individual and intersubject variance of β AR density and lymphocyte subpopulations over time in 10 normal subjects, studied on 3 to 5 different d always at approximately 9:00 a.m. over a 4 - to 12-wk period. Peripheral blood lymphocytes were isolated and β2-adrenergic receptor density was determined by specific binding of [I25I] - (-) iodopindolol, and lymphocyte subpopulations were measured by flow cytometry. Average receptors per lymphocyte were 776 ± 183. Whereas the absolute values of CD4 + % and CD8 + % cell concentrations varied little in individual subjects (coefficient of variation 9.5% and 11.1%, respectively), the individual β AR variance was greater (coefficient of variation 22.4%). However there was a significant correlation between β AR and CD4 + % and CD8 + % cell concentration (correlation coefficients: − 0.58, p < 0.001; + 0.51, p < 0.001, respectively). This information is relevant to interpretations of changes in peripheral β AR in humans.
β2-Agonist drugs at inhaled supratherapeutic doses or when given orally or parenterally alter peripheral lymphocyte β2-adrenoceptor density (βAR) and have demonstrable metabolic effects. However, it is not known whether these changes occur at therapeutic inhaled doses. We therefore studied the effects of therapeutic doses of inhaled albuterol in five asthmatic subjects (mean age 23.0 ±2.4 years) and six normal subjects (mean age 28.3 ± 3.3 years). Subjects were studied in a randomized, double-blind protocol in which each subject received either inhaled albuterol (270 μg four times daily) for 2 weeks followed by placebo or vice versa in two sequential 2-week periods separated by a 2-week washout period. In the asthmatics, baseline FEV1 increased significantly (p < 0.05) after 2 weeks of inhaled albuterol treatment compared to the initial visit and after 2 weeks of placebo (mean FEV1: 3.2 L ± 0.7 L, 2.9 L ± 0.5 L, and 3.0 L ± 0.7 L, respectively). Baseline peripheral lymphocyte βAR was not significantly different (p > 0.05) between the asthmatic (mean: 757 ± 176) and normal subjects (mean: 732 ± 251). However, in neither group was there any significant change (p > 0.05) in βAR or plasma potassium, insulin, or glucose, either acutely or after 2 weeks of albuterol therapy. The present study confirms that there is no difference in peripheral lymphocyte βAR between asthmatic and normal subjects and also shows that at therapeutic doses of inhaled albuterol, there are no significant changes in βAR or metabolic effects.
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