Abd-Elfattah A S, Hoehner J, Wechsler A S
Department of Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0532, USA.
Mol Cell Biochem. 1998 Mar;180(1-2):105-10.
The role of nucleoside transport in ischemia-reperfusion injury and arrhythmias has been well documented in various animal models using selective blockers. However, clinical application of nucleoside transport inhibitors remains to be demonstrated in humans. It is not known whether human heart has nucleoside transport similar to that of animals. The aim of this study is to pharmacologically identify the presence of nucleoside transport binding sites in the human myocardium compared to animals. Myocardial tissue was obtained from guinea pig left and right ventricle, canine left ventricle, human intraoperative right atrium and human cadaveric right atrium and right and left ventricles. Myocardial preparations were obtained from tissue samples after homogenized and a differential centrifugation. Equilibrium binding assays were performed using [3H]-p-nitrobenzylthioinosine (NBMPR) at room temperature in the presence or absence of non-radioactive NBMPR or other nucleoside transport blockers such as p-nitrobenzylthioguanosine dipyridamole, lidoflazine, papaverin, adenosine and doxorubcine. From saturation curves and inhibition kinetics, we determined the relative maximal binding (Bmax) and dissociation constant (Kd) of [3H]-NBMPR binding of human myocardial preparations. Results demonstrated that the fresh human myocardial preparations have a specific binding site for NBMPR with a Bmax of 283+/-32 fmol/mg protein and Kd of 0.56+/-0.12 nM. These values are lower than those obtained from guinea pigs (Bmax = 1440+/-187 fmol/mg protein and Kd = 0.21+/-0.03 nM) and canine atrium (Bmax 594+/-73 fmol/mg protein, and Kd = 1.12+/-0.22 nM). Displacement kinetics studies revealed the relative potencies (of certain unrelated drugs as follow: p-nitrobenzylthioguanosine > dipyridamole > lidoflazine > pavaverine > Diltazam > adenosine > doxyrubicin. It is concluded that human myocardium contains an active nucleoside transport site which may play a crucial role in post-ischemic reperfusion-mediated injury in a wide spectrum of ischemic syndromes.
在各种动物模型中，使用选择性阻滞剂已充分证明核苷转运在缺血再灌注损伤和心律失常中的作用。然而，核苷转运抑制剂在人体中的临床应用仍有待证实。目前尚不清楚人类心脏是否具有与动物类似的核苷转运。本研究的目的是通过药理学方法确定与动物相比，人类心肌中核苷转运结合位点的存在情况。心肌组织取自豚鼠左右心室、犬左心室、人类术中右心房以及人类尸体的右心房和左右心室。将组织样本匀浆并进行差速离心后获得心肌制剂。在室温下，使用[3H]-对硝基苄硫基肌苷（NBMPR）进行平衡结合试验，试验中存在或不存在非放射性NBMPR或其他核苷转运阻滞剂，如对硝基苄硫基鸟苷、双嘧达莫、利多氟嗪、罂粟碱、腺苷和阿霉素。通过饱和曲线和抑制动力学，我们确定了人类心肌制剂[3H]-NBMPR结合的相对最大结合量（Bmax）和解离常数（Kd）。结果表明，新鲜的人类心肌制剂对NBMPR具有特异性结合位点，Bmax为283±32 fmol/mg蛋白，Kd为0.56±0.12 nM。这些值低于豚鼠（Bmax = 1440±187 fmol/mg蛋白，Kd = 0.21±0.03 nM）和犬心房（Bmax 594±73 fmol/mg蛋白，Kd = 1.12±0.22 nM）的值。置换动力学研究揭示了某些无关药物的相对效力如下：对硝基苄硫基鸟苷>双嘧达莫>利多氟嗪>罂粟碱>地尔硫卓>腺苷>阿霉素。结论是，人类心肌含有一个活跃的核苷转运位点，这可能在广泛的缺血综合征的缺血后再灌注介导的损伤中起关键作用。
