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Characterization and Regulation of β 1 ‐Adrenergic Receptors in a Human Neuroepithelioma Cell Line
Author(s) -
Fishman Peter H.,
Nussbaum Elise,
Duman Ronald S.
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb08191.x
Subject(s) - receptor , agonist , medicine , endocrinology , iodocyanopindolol , biology , adrenergic receptor , forskolin , population , intrinsic activity , environmental health
Intact human neuroepithelioma SK‐N‐MC cells bound the β‐adrenergic antagonist (–)‐[ 3 H]‐CGP 12177 with a K D of 0.13 n M and a B max of 17,500 sites/cell. When the cells were exposed to β‐adrenergic agonists, they accumulated cyclic AMP in the following order of potency: isoproterenol norepinephrine > epinephrine, which is indicative of a β 1 ‐subtype receptor. Membranes prepared from the cells bound (–)‐3‐[ 125 I]iodocyanopindolol with a K D of 11.5 p M . Inhibition of agonist‐stimulated cyclic AMP production and competition binding experiments indicated that the β 1 ‐selective antagonists CGP 20712A and ICI 89,406 were much more potent than the β 2 ‐selective antagonist ICI 118,551. Analysis of the displacement curves indicated that the cells contained only β 1 ‐adrenergic receptors. Northern blot analysis of SK‐N‐MC mRNA using cDNA probes for the β 1 ‐ and β 2 ‐adrenergic receptors revealed the presence of a very strong β 1 ‐adrenergic receptor mRNA signal, while under the same conditions no β 2 ‐adrenergic receptor mRNA was observed. Thus, SK‐N‐MC cells appear to express a pure population of β 1 ‐adrenergic receptors. When the cells were exposed to isoproterenol, there was no observable desensitization during the first hour. After longer exposure, desensitization slowly occurred and the receptors slowly down‐regulated to 50% of control levels by 24 h. Other agents that elevate cyclic AMP levels, such as forskolin, cholera toxin, and cyclic AMP analogues, caused no or little substantial receptor loss.