Beta-adrenergic receptors in early human placenta characterization of [3H]-dihydroalprenolol binding

The binding characteristics of beta-adrenergic ligand ³H]-dihydroalprenolol (DHA) were determined in particulate membranes of early human placenta (8 – 12 weeks of gestation). ³H]-DHA binding to crude membrane fractions was rapid, reversible, saturable and linearly correlated with the membrane protein concentration. Scatchard analysis of saturation experiments showed a K_D of 2.80 ± 0.9 nM and a density of binding sites of 330.30 ± 93.5 fmol/mg protein. Agonist potency isoproterenol epinephrine norepinephrine indicated that early human placenta contains an adrenergic receptor of beta-2 subtype.