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  • 1
    ISSN: 1432-1041
    Keywords: Salbutamol ; male ; female ; β2-adrenoceptor ; menstrual cycle ; systemic responses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Extrapulmonary β2-adrenoceptor mediated responses to salbutamol were evaluated in 9 healthy female subjects during the follicular (day 2–4, Visit 1) and luteal (day 21–23, Visit 2) phases of the menstrual cycle, and were compared with those of 9 age-matched male controls. At each visit, salbutamol was given by intravenous infusion for 30 minutes at a dose of 0.2 mg · kg−1 · min−1. Plasma salbutamol concentration and responses in heart rate (HR), finger tremor (Tr), Q-T interval (Q-Tc), serum potassium (K), serum insulin (Ins) and serum glucose (Glu) were measured at baseline and at 10, 20 and 30 minutes after commencing the infusion. Comparisons were made between sexes and between visits for peak responses calculated as percentage change from baseline. Mean plasma salbutamol concentration (ng · ml−1) were not significantly different between males and females on Visit 1: 6.9 (95% CI 6.01, 7.82) vs 7.3 (95% CI 6.4, 8.3), or on Visit 2: 6.9 (95% CI 6.0, 7.8) vs 7.2 (95% CI 6.3, 8.1). On Visit 1, significantly greater responses were demonstrated in females, compared with males for K (as mean difference): 6 (95% CI 1, 11)%, Tr: 17 (95% CI 1, 33)%, Q-Tc: 8 (95% CI 2, 14)% and Ins: 276 (95% CI 71, 481)%. In addition, a significantly greater response was demonstrated in females on Visit 1 compared with males on Visit 2 for HR (as mean difference): 32 (95% CI 1, 63)%, and for Ins: 262 (95% CI 57, 467)%. Thus, despite no difference in plasma salbutamol concentrations, female subjects exhibited greater responsiveness to salbutamol compared with males during the follicular phase of the menstrual cycle. This suggests that in vivo, females have enhanced sensitivity of extrapulmonary β2-adrenoceptors.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: Asthma ; β2-Adrenoceptor ; lymphocyte ; subsensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary There is conflicting data in the literature as to whether subsensitivity of in-vivo β2-adrenoceptor (β2-AR) responses in patients with asthma is due to an endogenous defect of β2-AR or an effect of exogenous β2-agonist therapy. The purpose of the study was to compare in-vitro parameters of lymphocyte β2-AR function in eight age and sex matched normal [FEV1, 98 (2) % predicted] volunteers and asthmatic [FEV1, 60 (5) % predicted] subjects. The asthmatic group were washed out for 4 weeks by substituting inhaled β2-agonist therapy with ipratropium bromide, in order to exclude possible exogenous effects of β2-agonist exposure. Receptor binding affinity (Kd) and density (Bmax) were evaluated using (-)125I-iodocyanopindolol and maximal cAMP response (Emax) was assayed following stimulation with isoprenaline (10−4M). No significant differences were found between the normal and asthmatic group for Kd (pmol·l−1): 9.65 vs 10.2, Bmax (fmol/106 cells): 1.9 vs 1.6, or Emax (pmol/106 cells): 4.24 vs 4.85. Thus, parameters of β2-AR function are unaltered in asthmatic patients who have not been exposed to β2-agonists, suggesting that asthma is not associated with an endogenous defect of β2-AR.
    Type of Medium: Electronic Resource
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