Binding properties of beta-adrenergic receptors in early human fetal lung.
The characteristics of beta-adrenergic receptors in human fetal lung were examined using the beta-adrenoceptor antagonist 3H-dihydroalprenolol /DHA/. Steady-state binding was reached by 15 min at 25 degrees C, and the association and dissociation rate constants were 0.0422 nM-1 min-1 and 0.0874 min-1, respectively. From saturation experiments, Bmax of 82.0 +/- 38 fmol/mg protein and KD = 1.85 +/- 0.92 nM were calculated. Inhibition of 3H-DHA binding by beta-1 /metoprolol/ and beta-2 /zinterol, IPS-339, fenoterol/ selective drugs resulted in biphasic displacement curves with slope factors less than 1.0. Analysis of these curves revealed a beta-1: beta-2 ratio of 40:60 in human fetal lung. The presence of 3H-DHA binding sites in early human lung may have a developmental importance which is not yet understood.
Falkay
G
G
Németh
G
G
Kovács
L
L
D000318:Adrenergic beta-Agonists / Q000378:metabolism; D000319:Adrenergic beta-Antagonists / Q000378:metabolism; D001667:Binding, Competitive; D004082:Dihydroalprenolol / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008168:Lung / Q000196:embryology* / Q000378:metabolism; D011869:Radioligand Assay; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D006160:Guanosine Triphosphate