Interactions of radiolabelled ligands with specific receptors: an analysis.
The binding and displacement of beta-adrenoceptor blockers, [3H]propranolol ([3H]PRP) and [3H]dihydroalprenolol ([3H]DHA), were studied on isolated rat erythrocytes, their membranes and ghosts; the binding of [3H]DHA and a M-cholinoceptor blocker, [3H]quinuclidinylbenzylate ([3H]QNB), on cerebral cortex membranes. In all experiments, ligand-receptor interactions conformed to a model of two pools of receptors in the same effector system and the binding of two ligand molecules to the receptor. The results were similar for the displacement of [3H]PRP, [3H]DHA and [3H]QNB with propranolol, dihydroalprenolol and quinuclidinyl-benzylate, respectively. The parameters of [3H]PRP to beta-adrenoceptor binding for intact erythrocytes were: Kd1 = 0.74+/-0.07 nM, Kd2 = 14.40+/-0.41 nM, B1 = 24+/-2 unit/cell, B2 = 263+/-5 unit/cell; for ghosts, Kd1 = 0.70+/-0.17 nM, Kd2 = 19.59+/-2.59 nM, B1 = 9+/-1 fmol/mg protein, B2 = 39+/-4 fmol/mg protein. Receptor affinities were similar in erythrocytes and ghosts; on the ghost membrane, the number of receptors was considerably lower (B1 = 2 unit/cell, B2 = 6 unit/cell). The parameters of [3H]QNB to M-cholinoceptor binding of the cerebral cortex membrane were the following: Kd1 = 0.43 nM, Kd2 = 2.83 nM, B1 = 712 fmol/mg, B2 = 677 fmol/mg.
Manukhin
B N
BN
Institute of Developmental Biology, Russian Academy of Sciences, Moscow. manukhin@ibrran.msk.su
Nesterova
L A
LA
Smurova
E A
EA
Kichikulova
T P
TP
D000319:Adrenergic beta-Antagonists / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000378:metabolism; D004082:Dihydroalprenolol / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods; D008024:Ligands; D008297:Male; D018727:Muscarinic Antagonists / Q000378:metabolism; D011433:Propranolol / Q000378:metabolism*; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism
D000319:Adrenergic beta-Antagonists; D008024:Ligands; D018727:Muscarinic Antagonists; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D011813:Quinuclidinyl Benzilate; D011433:Propranolol