Godfraind T, Wibo M
Br J Pharmacol. 1985 Jun;85(2):335-40. doi: 10.1111/j.1476-5381.1985.tb08866.x.
The binding of [3H]-nitrendipine was studied in microsomal fractions isolated from guinea-pig ileal smooth muscle. Only one class of specific binding sites was detected, with a KD of 0.4 nM. For various dihydropyridine derivatives, including the stereoisomers of nimodipine and the 'Ca agonist' Bay K 8644, the potency for inhibition of [3H]-nitrendipine binding correlated well with the reported pharmacological potency in smooth muscle preparations. To establish the subcellular localization of [3H]-nitrendipine binding sites, untreated and digitonin-treated microsomal fractions were subfractionated by isopycnic density gradient centrifugation. The density distribution of [3H]-nitrendipine binding was markedly shifted by digitonin towards higher densities, as were the distributions of 5'-nucleotidase and [3H]-ouabain binding, whereas the distributions of NADPH:cytochrome c reductase and NADH:cytochrome c reductase were hardly modified by digitonin. It is concluded that most, if not all, [3H]-nitrendipine binding sites in guinea-pig ileal smooth muscle are present in the plasma membrane, in agreement with the postulated mode of action of dihydropyridines as inhibitors of plasmalemmal Ca channels.
在从豚鼠回肠平滑肌分离出的微粒体部分中研究了[3H]-尼群地平的结合情况。仅检测到一类特异性结合位点，解离常数（KD）为0.4 nM。对于各种二氢吡啶衍生物，包括尼莫地平的立体异构体和“钙激动剂”Bay K 8644，抑制[3H]-尼群地平结合的效力与在平滑肌制剂中报道的药理效力密切相关。为了确定[3H]-尼群地平结合位点的亚细胞定位，通过等密度梯度离心对未处理和经洋地黄皂苷处理的微粒体部分进行亚分级分离。洋地黄皂苷使[3H]-尼群地平结合的密度分布明显向更高密度偏移，5'-核苷酸酶和[3H]-哇巴因结合的分布也是如此，而NADPH：细胞色素c还原酶和NADH：细胞色素c还原酶的分布几乎未被洋地黄皂苷改变。得出的结论是，豚鼠回肠平滑肌中大多数（如果不是全部）[3H]-尼群地平结合位点存在于质膜中，这与二氢吡啶作为质膜钙通道抑制剂的假定作用模式一致。
