Binding of naloxone to human T lymphocytes

Abstract

Purified T lymphocytes have a specific binding site for naloxone, the opiate antagonist. The K D for the site was 50.6 ± 2.4 nM, while the Hill coefficient ( n) was 1.67 ± 0.16, indicating a degree of positive cooperativity of ligand binding. The bound naloxone was partially displaceable by various opiate agonists including morphine (56%), β-endorphin (61%), met 5- and leu 5-enkephalin (40% each), [ dala 2, dleu 5]-enkephalin (78%) and [ dala 2, dleu 5]-enkephalinamide (66%). Virtually all of the binding capacity was recovered in the particulate membrane fraction after sonic lysis of the cells. There was great interindividual variability in B max between samples, suggesting a possible mechanistic basis for the variability in drug action seen between different individuals.