Hagiwara Masafumi, Adachi-Akahane Satomi, Nagao Taku
Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Bunkyo, Japan.
Eur J Pharmacol. 2003 Apr 11;466(1-2):63-71. doi: 10.1016/s0014-2999(03)01547-4.
D-cis-[N-Methyl-3H]-3-(acetyloxy)-5-[2-[[2-(3,4-dimethoxyphenyl)ethyl]-methylamino]ethyl]-2,3-dihydro-2-(4-methoxyphenyl)-1,5-benzothiazepine-4(5H)-one ([3H]DTZ323), a novel 1,5-benzothiazepine radioligand, was characterized in a ligand-receptor binding study. Specific binding of [3H]DTZ323 to rabbit skeletal muscle T-tubule membranes was saturable and reversible. Scatchard analysis indicated a single binding site with a K(d) value of 1.4 and 1.8 nM at 25 and 37 degrees C, respectively. DTZ323 and diltiazem derivatives inhibited specific [3H]DTZ323 binding with a rank order of DTZ323>DTZ417 (quaternary ammonium derivative of DTZ323)>diltiazem>L-cis-DTZ323. The affinity of DTZ323 was 51 times higher than that of diltiazem. [3H]DTZ323 binding was also completely inhibited by verapamil and tetrandrine, thus revealing the unique nature of the diltiazem-binding site. Specific [3H]DTZ323 binding to crude guinea pig ventricular membranes was inhibited by diltiazem, DTZ323 and its derivatives with IC(50) values close to those previously reported for the blockade of L-type Ca(2+) channel currents. These results indicate that [3H]DTZ323 is a potent and selective radioligand for the diltiazem-binding site of L-type Ca(2+) channels.
新型1,5-苯并硫氮杂䓬放射性配体D-顺式-[N-甲基-3H]-3-(乙酰氧基)-5-[2-[[2-(3,4-二甲氧基苯基)乙基]-甲基氨基]乙基]-2,3-二氢-2-(4-甲氧基苯基)-1,5-苯并硫氮杂䓬-4(5H)-酮([3H]DTZ323)在配体-受体结合研究中得到了表征。[3H]DTZ323与兔骨骼肌T小管膜的特异性结合是可饱和且可逆的。Scatchard分析表明在25℃和37℃时分别有一个单一结合位点，解离常数(K(d))值分别为1.4和1.8 nM。DTZ323和地尔硫䓬衍生物抑制[3H]DTZ323特异性结合的顺序为DTZ323>DTZ417(DTZ323的季铵衍生物)>地尔硫䓬>L-顺式-DTZ323。DTZ323的亲和力比地尔硫䓬高51倍。维拉帕米和粉防己碱也完全抑制[3H]DTZ323结合，从而揭示了地尔硫䓬结合位点的独特性质。地尔硫䓬、DTZ323及其衍生物抑制[3H]DTZ323与豚鼠心室粗膜的特异性结合，其半数抑制浓度(IC(50))值与先前报道的L型钙通道电流阻断值相近。这些结果表明，[3H]DTZ323是L型钙通道地尔硫䓬结合位点的一种强效且选择性的放射性配体。
