Zernig G, Glossmann H
Institut für Biochemische Pharmakologie, Universität Innsbruck, Austria.
Biochem J. 1988 Jul 1;253(1):49-58. doi: 10.1042/bj2530049.
The 1,4-dihydropyridine (+/-)-[3H]nitrendipine reversibly binds to mitochondrial preparations from guinea-pig heart with a dissociation constant (Kd) of 593 +/- 77 nM and a maximum density of binding sites (Bmax.) of 1.75 +/- 0.27 nmol/mg of protein. This low-affinity high-capacity 1,4-dihydropyridine-binding site does not discriminate between the enantiomers of nitrendipine and is also found in mitochondrial membranes from guinea-pig liver (Kd 586 +/- 91 nM; Bmax. 0.36 +/- 0.04 nmol/mg of protein) and kidney (Kd 657 +/- 149 nM; Bmax. 0.56 +/- 0.12 nmol/mg of protein). Phenylalkylamines (e.g. verapamil) inhibit ( +/- )-[3H]nitrendipine binding with micromolar inhibition constants, but the benzothiazepine D-cis-diltiazem, a potent Ca2+-channel blocker, is without effect. The binding is heat-stable, shows a V-shaped pH-dependence with a minimum around pH 7.0, and is strongly dependent on ionic strength in the incubation medium. The cations La3+ greater than Cd2+ much greater than Co2+ greater than Ca2+ much greater than Ba2+ greater than Mg2+ greater than Li+ greater than Na+ and the anions NO3- greater than C1- greater than or equal to F- stimulate the binding, whereas PO4(3-) greater than SO4(2-) slightly inhibit it. The low-affinity ( +/- )-[3H]nitrendipine-binding site located on the mitochondrial inner membrane is biochemically and pharmacologically different from the 1,4-dihydropyridine-receptor domain of the L-type Ca2+ channel. Furthermore, it is not identical with any of the low-affinity 1,4-dihydropyridine-binding sites described so far.
1,4 - 二氢吡啶（±） - [³H]尼群地平可与豚鼠心脏的线粒体制剂可逆性结合，解离常数（Kd）为593±77 nM，结合位点的最大密度（Bmax.）为1.75±0.27 nmol/mg蛋白质。这种低亲和力、高容量的1,4 - 二氢吡啶结合位点不能区分尼群地平的对映体，在豚鼠肝脏的线粒体膜中也可发现（Kd 586±91 nM；Bmax. 0.36±0.04 nmol/mg蛋白质）以及肾脏（Kd 657±149 nM；Bmax. 0.56±0.12 nmol/mg蛋白质）。苯烷基胺类（如维拉帕米）以微摩尔级的抑制常数抑制（±） - [³H]尼群地平的结合，但苯并噻氮䓬类的D - 顺式地尔硫䓬，一种强效的钙通道阻滞剂，却没有作用。该结合对热稳定，呈现出V形的pH依赖性，在pH 7.0左右有最小值，并且强烈依赖于孵育介质中的离子强度。阳离子La³⁺＞Cd²⁺＞＞Co²⁺＞Ca²⁺＞＞Ba²⁺＞Mg²⁺＞Li⁺＞Na⁺以及阴离子NO₃⁻＞Cl⁻≥F⁻可刺激结合，而PO₄³⁻＞SO₄²⁻则稍有抑制作用。位于线粒体内膜上的低亲和力（±） - [³H]尼群地平结合位点在生化和药理学上与L型钙通道的1,4 - 二氢吡啶受体结构域不同。此外，它与目前所描述的任何低亲和力1,4 - 二氢吡啶结合位点都不相同。
