title: Characterization of alpha 1- and alpha 2-adrenoceptors directly associated with basolateral membranes from rat kidney proximal tubules.
abstract: We have used 2-(beta-(3-125iodo-4-hydroxyphenyl)-ethylaminoethyl)-tetr alo ne ([125I]HEAT or BE2254), an alpha 1-selective antagonist, and [3H]yohimbine, an alpha 2-selective antagonist, to demonstrate and characterize binding sites in basolateral membranes from rat kidney cortex. Parathyroid hormone (PTH) stimulated the adenylate cyclase activity of the basolateral membranes, whereas thyrocalcitonin, arginine vasopressin (AVP) and isoproterenol did not. Therefore, the basolateral membranes were probably derived from the proximal tubules. The specific binding of [125I]HEAT and [3H]yohimbine to basolateral membranes was rapid, reversible, saturable and of high affinity. The maximum densities of alpha 1- and alpha 2-receptors were 364 and 1130 fmoles/mg protein, indicating that the ratio of alpha 1- to alpha 2-adrenoceptors was about 1:3. The specific binding of [125I]HEAT and [3H]yohimbine to the basolateral membranes was displaced by various adrenergic agents in a manner that suggests that the labeled sites probably represent alpha 1- and alpha 2-adrenoceptors respectively. These results suggest that the binding sites of [125I]HEAT and [3H]yohimbine, which appear to be alpha 1- and alpha 2-adrenoceptors, exist in the basolateral membranes of the proximal tubules.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000032:analysis; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D007687:Kidney Tubules, Proximal / Q000032:analysis*; D007700:Kinetics; D008297:Male; D010627:Phenethylamines / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000032:analysis*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D013565:Sympatholytics / Q000494:pharmacology; D013566:Sympathomimetics / Q000494:pharmacology; D044024:Tetralones; D014316:Tritium; D015016:Yohimbine / Q000378:metabolism; D005723:gamma-Glutamyltransferase / Q000032:analysis
chemical_list: D007457:Iodine Radioisotopes; D010627:Phenethylamines; D011942:Receptors, Adrenergic, alpha; D013565:Sympatholytics; D013566:Sympathomimetics; D044024:Tetralones; D014316:Tritium; D015016:Yohimbine; C010652:BE 2254; D005723:gamma-Glutamyltransferase; D000254:Sodium-Potassium-Exchanging ATPase