5-Hydroxytryptamine uptake and imipramine binding sites in neurotumor NCB-20 cells.
NCB-20 cells (neuroblastoma X fetal Chinese hamster brain hybrids) are equipped with a [3H]5-hydroxytryptamine [( 3H]5-HT) uptake system and [3H]imipramine recognition sites. Approximately 80% of the radioactivity taken up by cells incubated with [3H]5-HT was identified with 5-HT. [3H]5-HT uptake was temperature-dependent, partially sodium-dependent, saturable (Km = 7.3 +/- 0.6 microM; Vmax = 2.0 +/- 0.6 pmol/min/mg), and inhibited by clomipramine, imipramine, fluoxetine, and desipramine, but not by iprindole, mianserin, or opipramol. Lineweaver-Burk plots showed a competitive type of inhibition by imipramine and fluoxetine. [3H]5-HT uptake was not inhibited by nisoxetine or benztropine. [3H]Imipramine binding sites had a KD of 12 +/- 2 nM and a Bmax of 22 +/- 7 pmol/mg protein. The binding was sodium-sensitive although to a lesser extent than that found with brain membranes. Imipramine binding was displaced by tricyclic antidepressants with the following order of potency: clomipramine greater than imipramine greater than fluoxetine greater than desipramine much greater than iprindole = mianserin greater than opipramol. These results suggest that imipramine binding sites are present together with the 5-HT uptake sites in NCB-20 cells and that these sites interact functionally but are different biochemically.
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001921:Brain / Q000166:cytology*; D002997:Clomipramine / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D003891:Desipramine / Q000494:pharmacology; D005473:Fluoxetine / Q000494:pharmacology; D006822:Hybrid Cells / Q000378:metabolism*; D007099:Imipramine / Q000378:metabolism* / Q000494:pharmacology; D007488:Iprindole / Q000494:pharmacology; D007700:Kinetics; D008803:Mianserin / Q000494:pharmacology; D009447:Neuroblastoma / Q000378:metabolism*; D009888:Opipramol / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000378:metabolism*
D005473:Fluoxetine; D008803:Mianserin; D012701:Serotonin; D007488:Iprindole; D009888:Opipramol; D002997:Clomipramine; D007099:Imipramine; D003891:Desipramine