Trophoblastic cells of the hydatidiform mole contain a beta 1-subtype adrenergic receptor

Both beta 1- and beta 2-adrenergic receptors have been previously described in normal human placental homogenates; the cells upon whose surface membranes these receptors reside have not been identified. In order to show that a beta 1-adrenergic receptor is present on trophoblastic cells, the cells which mediate maternal-fetal transport and produce placental hormones, beta-adrenergic receptors were demonstrated in membrane fractions of human hydatidiform mole. Microscopic sections of the mole samples used demonstrated edematous villi lined by trophoblastic cells with minimal nontrophoblastic (stromal or vascular) contamination compared with placenta. (--)-[3H]Dihydroalprenolol [(--)-[3H]DHA] binding to molar membranes was reversible and saturable to a single class of sites (Kd = 0.97 +/- 0.12 nM; n = 7; maximum binding capacity, 72.9 +/- 6.4 fmol/mg protein). (--)-[3H]DHA binding was associated with catecholamine-stimulated adenylate cyclase activity. Agonist competition for the molar beta-adrenergic receptor showed the order of potency to be (--)isoproterenol much greater than norepinephrine = epinephrine, characteristic of a beta 1-adrenergic receptor subtype. Competition for (--)-[3H]DHA binding to trophoblastic membranes by the beta-adrenergic receptor subtype-specific agents metoprolol (beta 1 selective) and zinterol (beta 2 selective) was also characteristic of a homogeneous subtype of beta 1-adrenergic receptors. Because beta 1-adrenergic receptors alone were seen on trophoblast cells, the beta 2-adrenergic receptor in placenta must reside on nontrophoblastic elements (stromal or vascular endothelium). No differences in beta-adrenergic receptor binding were seen related with ploidy (2 or 3 N), the presence or absence of a fetus, or the progression of the mole to choriocarcinoma. Two choriocarcinoma cell lines, BeWo and JEG-3, however, showed no specific (--)-[3H]DHA binding. Human trophoblast contains beta 1-adrenergic receptors coupled to catecholamine-sensitive adenylate cyclase, supporting a role for catecholamines in the regulation of placental metabolism.