The hydrophilic ligand 3H-CGP 12177 was used to measure β-adrenergic receptors on intact human mononuclear leukocytes (MNLs). A single homogeneous class of receptor sites was found, with K(D) value of 0.71 ± 0.04 nmol/L and B(max) of 3.0 ± 0.4 fmol/106 cells (mean ± SEM; n = 12). The receptor affinity (K(D)) and density (B(max)) were similar when measured on MNLs, purified lymphocytes, and a T-lymphocyte-enriched population from the same individual. Preincubation of intact MNLs with 1 μmol/L isoproterenol at 37°C for 20 minutes reduced the number of surface receptors, measured by 3H-CGP 12177 binding at 4° C for 20 hours, by ~ 70% (receptor internalization) without affecting K(D). This effect was reversible, and surface receptors completely reappeared when binding was investigated at 37°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°C but was partially or completely lost from MNLs prepared at 20°C.
|Number of pages||9|
|Journal||The Journal of Laboratory and Clinical Medicine|
|Publication status||Published - 1986|
ASJC Scopus subject areas
- Pathology and Forensic Medicine