title: The binding of agonists and antagonists to rat lung beta-adrenergic receptors as investigated by thermodynamics and structure-activity relationships.
abstract: Interaction of several agonists and antagonists with the relevant beta receptor were studied in vitro using rat lung membranes as beta-adrenergic receptor source. The influence of temperature, between 4 degrees C and 37 degrees C, on the ability of beta-adrenergic agonists and antagonists to displace (-)-[125I]iodocyanopindolol from beta-adrenergic receptors was checked. Thermodynamic parameters were calculated from the Kj values thus obtained. Lipophilicity of the twenty molecules was also measured using a RP-HPLC method. The results obtained show: the density of receptors was not affected by the temperature but their affinity for the twenty agonists and antagonists increased with decreasing temperature; the binding of agonists is enthalpy driven while that of antagonists is entropy driven, with the exception of the lipophilic agonist dobutamine; a single relationship between entropy and lipophilicity exists for all twenty compounds and would suggest that molecular structure and physicochemical properties account for the thermodynamics of binding.
mesh_terms: D000318:Adrenergic beta-Agonists / Q000378:metabolism*; D000319:Adrenergic beta-Antagonists / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D066298:In Vitro Techniques; D050356:Lipid Metabolism; D008168:Lung / Q000378:metabolism*; D008297:Male; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012995:Solubility; D013816:Thermodynamics
chemical_list: D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta