Henneberry R C, Jahangeer S, Lysko P G
Biochem Pharmacol. 1986 Aug 15;35(16):2687-92. doi: 10.1016/0006-2952(86)90176-0.
We have demonstrated that the rat pituitary tumor cell line GH3 has a carrier-mediated active transport system for the beta-adrenergic antagonist dihydroalprenolol (DHA). Transport of DHA in GH3 was saturable, with an apparent Km of 1.4 microM, was temperature and pH dependent, and was inhibited by the ionophore monensin and the amine transport inhibitor reserpine. Propranolol competed for DHA transport, but not in a stereoselective fashion. The tricyclic antidepressant imipramine also competed for DHA transport, but catecholamines or serotonin did not. This amine transport system in GH3 cells appeared to be identical to the one we recently described in several other cell types; however, analysis in those cells was complicated by the fact that they contain beta-adrenergic receptors which bind beta-adrenergic ligands. In this report we show that GH3 cells do not possess detectable beta-adrenergic receptors, based on their inability to bind the partial agonist CGP-12177, their inability to bind nanomolar concentrations of DHA in a saturable, stereospecific manner, and their failure to produce cAMP in response to stimulation by beta-adrenergic agonists. Characterization of the amine transport system in GH3 cells clearly distinguishes it from receptor-mediated phenomena and should facilitate our efforts to fully understand its mechanism and significance.
我们已经证明，大鼠垂体肿瘤细胞系GH3具有一种载体介导的主动转运系统，用于转运β-肾上腺素能拮抗剂二氢阿普洛尔（DHA）。DHA在GH3细胞中的转运具有饱和性，表观Km为1.4微摩尔，依赖于温度和pH值，并且受到离子载体莫能菌素和胺转运抑制剂利血平的抑制。普萘洛尔竞争DHA的转运，但不具有立体选择性。三环类抗抑郁药丙咪嗪也竞争DHA的转运，但儿茶酚胺或5-羟色胺则不然。GH3细胞中的这种胺转运系统似乎与我们最近在其他几种细胞类型中描述的系统相同；然而，在那些细胞中的分析由于它们含有能结合β-肾上腺素能配体的β-肾上腺素能受体这一事实而变得复杂。在本报告中，我们表明，基于GH3细胞无法结合部分激动剂CGP - 12177、无法以饱和、立体特异性方式结合纳摩尔浓度的DHA以及它们在β-肾上腺素能激动剂刺激下无法产生环磷酸腺苷，GH3细胞不具有可检测到的β-肾上腺素能受体。对GH3细胞中胺转运系统的表征清楚地将其与受体介导的现象区分开来，并且应该有助于我们全面了解其机制和意义的努力。
