Agonist-induced beta-adrenergic receptor internalization on intact human mononuclear leukocytes: effect of temperature of mononuclear leukocyte separation.
The hydrophilic ligand 3H-CGP 12177 was used to measure beta-adrenergic receptors on intact human mononuclear leukocytes (MNLs). A single homogeneous class of receptor sites was found, with KD value of 0.71 +/- 0.04 nmol/L and Bmax of 3.0 +/- 0.4 fmol/10(6) cells (mean +/- SEM; n = 12). The receptor affinity (KD) and density (Bmax) were similar when measured on MNLs, purified lymphocytes, and a T-lymphocyte-enriched population from the same individual. Preincubation of intact MNLs with 1 mumol/L isoproterenol at 37 degrees C for 20 minutes reduced the number of surface receptors, measured by 3H-CGP 12177 binding at 4 degrees C for 20 hours, by approximately 70% (receptor internalization) without affecting KD. This effect was reversible, and surface receptors completely reappeared when binding was investigated at 37 degrees C for 40 minutes. Receptor internalization was similar when either isolated MNLs or whole blood was incubated with isoproterenol. Agonist-induced receptor internalization was stable during MNL isolation from whole blood at 4 degrees C but was partially or completely lost from MNLs prepared at 20 degrees C.
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D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D002469:Cell Separation; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D007962:Leukocytes / Q000032:analysis*; D008297:Male; D011412:Propanolamines / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000032:analysis*; D013696:Temperature; D014316:Tritium
D000318:Adrenergic beta-Agonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D014316:Tritium; D007545:Isoproterenol; C033394:CGP 12177