title: Evidence for intravesicular beta-adrenergic receptors in membrane fractions from desensitized cells: binding of the hydrophilic ligand CGP-12177 only in the presence of alamethicin.
abstract: Two fractions of beta-adrenergic receptors have been separated from desensitized C62B cells by centrifugation on a sucrose gradient. Using two beta-adrenergic receptor (beta AR) antagonists, 125I-iodopindolol and (3H)CGP-12177, the different binding characteristics of these fractions have been investigated. While iodopindolol binds to beta AR both in a light (30% sucrose) and a heavy (45-50% sucrose) peak, CGP-12177 binds only to those in the heavy peak. Incubation of these two gradient fractions with the antibiotic alamethicin selectively increases the binding of CGP-12177 only in the light peak. This result suggests that the desensitization-induced light peak beta AR exist on the inside of vesicles. The hydrophilic ligand CGP-12177 is capable of reaching these receptors only through alamethicin-formed pores.
mesh_terms: D000408:Alamethicin / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D005910:Glioma / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D010869:Pindolol / Q000031:analogs & derivatives* / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology*; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D000408:Alamethicin; C029247:3-iodopindolol; D010869:Pindolol; D007545:Isoproterenol; C033394:CGP 12177