Millar D B, Mazorow D L, Hough C
New Ideas Co., Rockville, MD 20852, USA.
J Neuroimmunol. 1997 Sep;78(1-2):8-18. doi: 10.1016/s0165-5728(97)00078-7.
Beta-endorphin and naloxone bind to Jurkat cell membrane preparations and can mutually displace each other from membrane binding sites. Tetraethylammonium ion, a potassium channel blocker, competitively displaces beta-endorphin and naloxone from membrane binding sites. Mitogen stimulated calcium ion flux is inhibited by tetraethyl ammonium and this inhibition is relieved by naloxone. With data derived from whole cell calcium ion flux studies, we accurately calculated the competitive displacement of beta-endorphin and naloxone from membrane preparations by tetraethylammonium thus showing that the action of these agents on potassium channels does not require second messengers. Using the resuspension induced ion flux technique, we find that beta-endorphin competes against naloxone for binding to Jurkat cells and naloxone competes against charybdotoxin, a potassium channel inhibitor, which like tetraethylammonium, is known to bind to the outer vestibule of the channel. Patch clamp electrophysiological studies show that beta-endorphin and naloxone exert complex actions on potassium channels in the presence or absence of mitogens. We conclude that one molecule of beta-endorphin or naloxone, but not both at the same time, bind to an area near the charybdotoxin/tetraethylammonium binding locus of Jurkat potassium channels.
β-内啡肽和纳洛酮可与Jurkat细胞膜制剂结合，并且能从膜结合位点上相互取代对方。钾通道阻滞剂四乙铵离子可竞争性地将β-内啡肽和纳洛酮从膜结合位点上取代下来。丝裂原刺激的钙离子通量受到四乙铵的抑制，而这种抑制作用可被纳洛酮缓解。根据全细胞钙离子通量研究获得的数据，我们准确计算出四乙铵对β-内啡肽和纳洛酮从膜制剂上的竞争性取代，从而表明这些试剂对钾通道的作用不需要第二信使。使用重悬诱导离子通量技术，我们发现β-内啡肽与纳洛酮竞争结合Jurkat细胞，而纳洛酮与钾通道抑制剂蝎毒素竞争，蝎毒素与四乙铵一样，已知可结合通道的外部前庭。膜片钳电生理研究表明，无论有无丝裂原，β-内啡肽和纳洛酮对钾通道都有复杂的作用。我们得出结论，一个β-内啡肽或纳洛酮分子，但不是同时两者，会结合到Jurkat钾通道的蝎毒素/四乙铵结合位点附近的区域。
