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Radioligand binding characteristics of β 2 –adrenoceptors of cultured melanoma cells
Author(s) -
STEINKRAUS V.,
NOSE MONIKA,
MENSING H.,
KÖRNER CHRISTA
Publication year - 1990
Publication title -
british journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.304
H-Index - 179
eISSN - 1365-2133
pISSN - 0007-0963
DOI - 10.1111/j.1365-2133.1990.tb01843.x
Subject(s) - radioligand , radioligand assay , alprenolol , isoprenaline , antagonist , propranolol , beta (programming language) , chemistry , endocrinology , receptor , medicine , potency , cell culture , pharmacology , biology , biochemistry , stimulation , in vitro , genetics , computer science , programming language
summary The existence of β‐adrenoceptors on intact cells of the human malignant melanoma cell line A‐ 375 was investigated using the binding properties of the tritiated radioligand (‐)‐[ 3 H]CGP‐ 12177, a hydrophilic non‐selective β‐adrenoceptor antagonist. Displacement experiments of the radioligand from its binding site were performed with antagonists and agonists to determine the β‐adrenoceptor subtype selectivity. The binding of (‐)‐[ 3 H]CGP‐12177 was saturable, of high affinity ( K d = 0.025 nmol/1, n = 12) and was rapid and readily reversible. The maximal number of binding sites (B max ) was 33.5 ± 1.9 fmol/10 7 cells or 2018 ± 114 receptors per cell. β‐adrenoceptor antagonists inhibited binding of the radioligand with monophasic displacement curves. IC 50 values were (nmol/l): propranolol (non‐selective) 2.82, alprenolol (non‐selective) 2.0, ICI 118,551 (β 2 ‐selective) 3.5 and bisoprolol (β 1 ‐selective) 2200. Agonists inhibited binding in the order of potency of isoprenaline > adrenaline > noradrenaline. It is concluded that cells of the melanoma cell line A‐375 contain a homogeneous population of β 2 ‐ adrenoceptors.