Endocytosis of beta-adrenergic ligands by rat liver. Comparison of beta-adrenergic receptor and adenylate cyclase distribution in endosome and plasma-membrane fractions.
The internalization of beta-adrenergic receptors was investigated in rat livers perfused with an agonist ([3H]isoprenaline) or an antagonist ([125I]iodocyanopindolol). Analytical centrifugation of liver homogenates indicated that the ligands were transferred rapidly to endosomal and lysosomal positions in sucrose gradients. Endosome fractions contained beta-adrenergic binding sites, but adenylate cyclase activity was low and poorly activated by isoprenaline. The results indicate that the receptor-regulatory-protein-adenylate cyclase complex was disassembled during uptake of beta-adrenergic ligands, with the adenylate cyclase being retained at the plasma membrane.
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D004705:Endocytosis; D005260:Female; D020120:Iodocyanopindolol; D007545:Isoproterenol / Q000378:metabolism; D008024:Ligands; D008099:Liver / Q000378:metabolism*; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
D008024:Ligands; D011943:Receptors, Adrenergic, beta; D020120:Iodocyanopindolol; D010869:Pindolol; D000262:Adenylyl Cyclases; D007545:Isoproterenol