Beta-adrenoceptors in human airway tissue: relationship between functional responsiveness and receptor number.
Functional organ bath experiments and radiolabelled ligand binding studies were used to investigate the relationship between beta-adrenoceptor-mediated relaxation and the total number of beta-adrenoceptors in human lung parenchymal tissue and bronchial tissue. Sensitivity to the beta-adrenoceptor agonist isoprenaline (pD2) varied almost 10-fold (pD2 values 6.00 to 6.85) for lung parenchymal preparations and 35-fold for bronchial preparations (pD2 values 6.16 to 7.67) between patients. The total number of [3H] DHA labelled beta-adrenoceptors (Bmax) varied almost 6-fold for lung parenchymal membrane preparations (Bmax 164 to 936 fmol/mg protein) and less than 2-fold for bronchial tissue membrane preparations (Bmax 188 to 342 fmol/mg protein) between patients. Comparison of sensitivity to isoprenaline and beta-adrenoceptor number for lung parenchymal tissue from the same patient demonstrated a negative correlation (r = -0.80 [95% confidence intervals: -0.13, -0.96], 6 d.f., P less than 0.05), suggesting that beta-adrenoceptor-mediated sensitivity of lung parenchymal tissue is inversely related to the number of beta-adrenoceptors. However, there was an absence of correlation between sensitivity to isoprenaline and beta-adrenoceptor number in bronchial tissue from the same patient. Thus, the findings of the present study do not support the possibility of a direct relationship between the beta-adrenoceptor-mediated responsiveness and the beta-adrenoceptor number of human airway preparations.
Whicker
S D
SD
Department of Pharmacology, University of Sydney, NSW, Australia.
Lummis
S C
SC
Black
J L
JL
D000368:Aged; D001980:Bronchi / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008168:Lung / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011869:Radioligand Assay; D011943:Receptors, Adrenergic, beta / Q000032:analysis* / Q000378:metabolism
D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol