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

1. [3H]石蜡毒素与牛肾上腺髓质细胞特异性结合，平衡解离常数（Kd）为5.8 nM，最大结合容量（Bmax）为427.2 fmol /107个细胞（124.2 fmol / mg细胞蛋白）。在牛肾上腺髓细胞中，三环（丙咪嗪、阿米替林和去甲替林）和四环（马普替林和米安色林）抗抑郁药抑制碳巴酚（IC_<50 >4 -96 muM）和缬曲定（IC_<50 >0 -17 muM）引起的^<22>Na、^<45>Ca的内流和儿茶酚胺的分泌。抗抑郁药不抑制高钾诱导的45Ca内流和儿茶酚胺分泌。[^3H]丙咪嗪的特异性结合K_d值分别为13.3和165.0 muM。三环和四环抗抑郁药（但不包括胆碱能药物和神经毒素）竞争[^3H]丙咪嗪结合。这些结果表明，三环和四环抗抑郁药结合两个位点，这些位点在功能上与尼古丁受体相关的离子通道和电压依赖性的Na通道相关，并抑制Na内流。抑制Na内流可导致Ca内流减少，并可减少由于carbachol和veratradine引起的儿茶酚胺分泌。在牛肾上腺髓细胞中，苯环利定能抑制碳巴酚（IC_<50 b> 7.0-10.0 muM）和veratridine （IC_<50> 56.0-60.0 muM）引起的^<22>Na内流、^<45>Ca内流、^<86>Rb外排和儿茶酚胺分泌，但对高钾诱导的^<45>Ca内流和儿茶酚胺分泌有影响。[^3H]苯环利啶结合的Scatchard分析显示两个不同的K_2值（4.3和77.4 muM）。[^3H]胆碱能药物和神经毒素均不抑制苯环合。结果表明：(1)苯环利定不抑制电压依赖性Ca通道和Ca依赖性K通道；(2) phencyclodine结合两个位点，每个位点都与烟碱受体-离子通道复合物和电压依赖性Na通道相连，并抑制Na内流。抑制钠内流导致减少钙内流，钾外排和儿茶酚胺分泌由碳巴酚和缬草碱引起。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