title: Radioligand binding characterization of beta-adrenergic receptors in the protozoa Trypanosoma cruzi.
abstract: A direct radioligand binding technique utilizing the beta-adrenergic antagonist [3H]dihydroalprenolol was employed in the identification and characterization of Trypanosoma cruzi beta-adrenergic receptors. [3H]DHA binding was saturable (Bmax = 1.5 pmol/10(6) cells) with an apparent equilibrium dissociation constant (Kd) of 127 nM. Binding of [3H]DHA was displaced by propranolol in a concentration-dependent manner. The relative potency order of adrenergic ligands in displacing [3H]DHA binding was: propranolol greater than or equal to alprenolol greater than epinephrine. 5-Hydroxytryptamine, phentolamine and catechol had no effect. The experimental results support the suggestion that beta-adrenergic receptors are present in the pathogenic protozoa Trypanosoma cruzi.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D004082:Dihydroalprenolol / Q000378:metabolism; D007700:Kinetics; D011869:Radioligand Assay; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D014349:Trypanosoma cruzi / Q000378:metabolism*
chemical_list: D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol