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Identification of nucleoside transport binding sites in the human myocardium
Journal article   Peer reviewed

Identification of nucleoside transport binding sites in the human myocardium

Anwar-saad Abd-elfattah, Jeff Hoehner and Andrew Wechsler
Molecular and cellular biochemistry, v 180(1-2), pp 105-110
01 Mar 1998
PMID: 9546636

Abstract

Binding sites
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 [^sup 3^H]-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 (B^sub max^) and dissociation constant (K^sub d^) of [^sup 3^H]-NBMPR binding of human myocardial preparations. Results demonstrated that the fresh human myocardial preparations have a specific binding site for NBMPR with a B^sub max^ of 283 ± 32 fmol/mg protein and K^sub d^ of 0.56 ± 0.12 nM. These values are lower than those obtained from guinea pigs (B^sub max^ = 1440 ± 187 fmol/mg protein and K^sub d^ = 0.21 ± 0.03 nM) and canine atrium (B^sub max^ 594 ± 73 fmol/mg protein, and K^sub d^ = 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.[PUBLICATION ABSTRACT]

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Cell Biology
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