Characterization of membrane proteins involved in catecholamine secretion and analysis on drug action in cultured adrenal medullary cells.

1.[~3H]Saxitoxin与牛肾上腺髓质细胞的结合平衡解离常数(Kd)为5.8nM，最大结合容量(Bmax)为427.2 fmmos/107cell(124.2 fmmols/mg cell Protein)。在牛肾上腺髓质细胞中，三环(丙咪嗪、阿米替林和去甲替林)和四环(麦普替林和米安色林)抗抑郁剂可抑制卡巴胆碱(IC_&lt；50&gt；14-96um)和藜芦碱(IC_&lt；50&gt；10-17um)引起的钙内流和儿茶酚胺的分泌。抗抑郁药不能抑制高钾引起的45Ca内流和儿茶酚胺的分泌。丙咪嗪的特异性结合有两个不同的Kd值(13.3um和165.0微米)。三环和四环抗抑郁药(但不是胆碱能药物和神经毒素)竞争[~3H]丙咪嗪的结合。这些结果表明，三环和四环抗抑郁药结合在两组与烟碱受体相关离子chan…功能相关的位点上。更多的NEL和具有电压依赖的Na通道，并抑制Na内流。抑制Na内流导致卡巴胆碱和藜芦碱引起的钙内流和儿茶酚胺分泌减少。在牛肾上腺髓质细胞中，苯环利定可抑制卡巴胆碱和藜芦碱引起的钙内流、Rb外流和儿茶酚胺的分泌，但对高钾诱导的内流和儿茶酚胺的分泌有抑制作用。对苯环利定结合的Scatchard分析显示有两个不同的K2值(4.3和77.4um)。胆碱能药物和神经毒素不抑制苯环结合。结果提示：(1)苯环利定对电压依赖性钙通道和钙依赖性钾通道无抑制作用；(2)苯环利定与烟碱受体-离子通道复合体和电压依赖性钠通道结合，并抑制钠内流。苯环磷胆碱抑制Na内流，减少卡巴胆碱和藜芦碱引起的Ca内流、K外流和儿茶酚胺分泌。较少

1. [3H]Saxitoxin bound specifically to bovine adrenal medullary cells with equilibrium dissociation constant (Kd) of 5.8 nM and maximum binding capacity (Bmax) of 427.2 fmols/107 cells (124.2 fmols/ mg cell protein).2. In bovine adrenal medullary cells, tricyclic (imipramine, amitriptyline and nortriptyline) and tetracyclic (maprotiline and mianserin) antidepressants inhibited influx of ^<22>Na, ^<45>Ca and secretion of catecholamines caused by carbachol (IC_<50> 14-96 muM) and by veratridine (IC_<50> 10-17 muM). Antidepressants did not suppress high K-induced 45Ca influx and catecholamine secretion. Specific binding of [^3H]imipramine had two different K_d values (13.3 and 165.0 muM). Tricyclic and tetracyclic antidepressants (but not cholinergic drugs and neurotoxins) competed for [^3H]imipramine binding. These results suggest that tricyclic and tetracyclic antidepressants bind to two populations of sites which are functionally associated with nicotinic receptor-associated ionic chan … More nels and with voltage-dependent Na channels, and inhibit Na influx. Inhibi on of Na influx leads to the reduction of Ca influx and catecholamine secretion due to carbachol and veratridine.3. In bovine adrenal medullary cells, phencyclidine inhibited influx of ^<22>Na, ^<45>Ca, efflux of ^<86>Rb and secretion of catecholamines caused by carbachol (IC_<50> 7.0-10.0 muM) and by veratridine (IC_<50> 56.0-60.0 muM), but had to effect on high K-induced ^<45>Ca influx and catecholamine secretion. Scatchard analysis of [^3H]phencyclidine binding showed two different K_2 values (4.3 and 77.4 muM). [^3H]phencycliding binding was not inhibited by cholinergic drugs and neurotoxins. The results suggest that (1) phencyclidine does not inhibit voltage-dependent Ca channels and Ca-dependent K channels; (2) phencyclodine binds to two populations of sites, each of which is linked to nicotinic receptor-ion channel complex and to voltage-dependent Na channels, and inhibits Na influx. Inhibition of Na influx by phencyclodine leads to the redution of Ca influx, K efflux and catecholamine secretion caused by carbachol and by veratridine. Less