Nucleoside transport in heart: species differences in nitrobenzylthioinosine binding, adenosine accumulation, and drug-induced potentiation of adenosine action

1984 ◽  
Vol 62 (1) ◽  
pp. 31-37 ◽  
Author(s):  
Evan F. Williams ◽  
Philip H. Barker ◽  
A. S. Clanachan
Keyword(s):  
Guinea Pig ◽  
Rat Heart ◽  
Binding Capacity ◽  
Specific Binding ◽  
Nucleoside Transport ◽  
Inotropic Action ◽  
Guinea Pig Heart ◽  
Cardiac Membranes ◽  
Nucleoside Transport Inhibitors ◽  
Transport Inhibitors

The site-specific binding of the potent and selective nucleoside transport inhibitor, [3H]nitrobenzylthioinosine (NBMPR), to the nucleoside transport system of cardiac membranes of several species was investigated. The affinity of [3H]NBMPR for these sites ranged from 0.03 nM in rat to 0.78 nM in dog. The maximal binding capacity of cardiac membranes for [3H]NBMPR was also species dependent and was greatest in bovine and guinea pig heart (2551 and 1700 fmol/mg protein, respectively) and least in rat (195 fmol/mg protein). The affinities of recognized nucleoside transport inhibitors and benzodiazepines for these transport inhibitory sites in guinea pig and rat heart were estimated by studying the inhibition of the site-specific binding of [3H]NBMPR in competition experiments. These values were compared with their inhibitory effects on the transporter-dependent accumulation of [3H]adenosine in guinea pig and rat cardiac muscle segments and with their ability to potentiate the negative inotropic action of adenosine in electrically driven guinea pig and rat left atria. In guinea pig heart, the recognized nucleoside transport inhibitors and benzodiazepines had an order of affinity (dilazep > hydroxynitrobenzylthioguanosine > dipyridamole > hexobendine [Formula: see text] lidoflazine [Formula: see text] flunitrazepam > diazepam > lorazepam > flurazepam) for the NBMPR site which was similar to those for the inhibition of [3H]adenosine accumulation and for potentiation of adenosine action. In contrast, in rat heart, where the maximal binding capacity of [3H]NBMPR was lower (eightfold), the nucleoside transporter dependent accumulation of [3H]adenosine was also lower (sixfold) and the negative inotropic action of adenosine was not significantly potentiated. Furthermore, NBMPR sites in rat heart displayed a significantly lower affinity for hexobendine, dipyridamole, and lidoflazine relative to sites in guinea pig hearts. These data indicate that significant differences in cardiac nucleoside transport systems exist among species with respect to both membrane density and drug affinity. Such differences influence the ability of transport inhibitors to modify adenosine action in these tissues.

scholarly journals [3H]dipyridamole binding to nucleoside transporters from guinea-pig and rat lung

1986 ◽  
Vol 240 (3) ◽  
pp. 879-883 ◽  
Author(s):  
M M Shi ◽  
J D Young
Keyword(s):  
Guinea Pig ◽  
Nucleoside Transporters ◽  
Nucleoside Transport ◽  
Affinity Binding ◽  
Nucleoside Transporter ◽  
High Affinity Binding ◽  
High Affinity ◽  
Nucleoside Transport Inhibitors ◽  
Transport Inhibitors ◽  
Low Sensitivity

Membranes from guinea-pig lung exhibited high-affinity binding of [3H]dipyridamole, a potent inhibitor of nucleoside transport. Binding (apparent KD 2 nM) was inhibited by the nucleoside-transport inhibitors nitrobenzylthioinosine (NBMPR), dilazep and lidoflazine and by the transported nucleosides uridine and adenosine. In contrast, there was no detectable high-affinity binding of [3H]dipyridamole to lung membranes from the rat, a species whose nucleoside transporters exhibit a low sensitivity to dipyridamole inhibition. Bmax. values for high-affinity binding of [3H]dipyridamole and [3H]NBMPR to guinea-pig membranes were similar, suggesting that these structurally unrelated ligands bind to the NBMPR-sensitive nucleoside transporter with the same stoichiometry.

Photoaffinity labeling of adenosine transporter in cardiac membranes with nitrobenzylthioinosine

1984 ◽  
Vol 246 (5) ◽  
pp. H710-H715
Author(s):  
K. F. Kwan ◽  
S. M. Jarvis
Keyword(s):  
Molecular Weight ◽  
Guinea Pig ◽  
Binding Capacity ◽  
Specific Inhibitor ◽  
Nucleoside Transport ◽  
Covalent Attachment ◽  
Radical Scavenger ◽  
Apparent Dissociation Constant ◽  
Cardiac Membranes ◽  
Adenosine Receptor Agonist

The kinetic and molecular properties of the adenosine transporter in guinea pig cardiac membranes were studied using nitrobenzylthioinosine (NBMPR), a potent and specific inhibitor of nucleoside transport. [3H]-NBMPR bound tightly but reversibly to guinea pig cardiac membranes (apparent dissociation constant 0.24 +/- 0.07 nM; maximum binding capacity 1.24 +/- 0.45 pmol of NBMPR bound/mg protein). Reversible high-affinity [3H]NBMPR binding was inhibited in an apparent competitive manner by adenosine (apparent inhibition constant 0.14 mM). L-N-phenylisopropyladenosine (L-PIA) had no effect on NBMPR binding. Exposure of cardiac membranes in the presence of [3H]-NBMPR and dithiothreitol, a free-radical scavenger, to ultraviolet light resulted in covalent incorporation of 3H into polypeptides of apparent molecular weight 66,000-50,000. Covalent attachment of [3H]NBMPR under equilibrium binding conditions was inhibited by adenosine, nitrobenzylthioguanosine , and dipyridamole but was unaffected by the adenosine receptor agonist L-PIA. These data suggest that the photolabeled molecular weight protein (apparent mol wt 66,000-50,000) is involved in adenosine permeation by guinea pig cardiac membranes.

Affinity of calcium channel inhibitors, benzodiazepines, and other vasoactive compounds for the nucleoside transport system

1985 ◽  
Vol 63 (10) ◽  
pp. 1302-1307 ◽  
Author(s):  
James R. Hammond ◽  
Evan F. Williams ◽  
Alexander S. Clanachan
Keyword(s):  
Guinea Pig ◽  
Calcium Channel ◽  
Transport System ◽  
Human Erythrocytes ◽  
Nucleoside Transport ◽  
Rat Tissues ◽  
High Affinity ◽  
Cardiac Membranes ◽  
Transport Inhibitors ◽  
Calcium Channel Inhibitors

There is evidence to suggest that several different groups of drugs including the so-called coronary vasodilators, benzodiazepines, and calcium channel inhibitors may owe their vasoactivity, in part, to the potentiation of the vasorelaxant effects of endogenous adenosine. To measure the affinity of some of these agents for the membrane-located nucleoside transport system, competition binding assays have been performed using the high-affinity radioligand [3H]nitrobenzylthioinosine (NBMPR). Experiments were performed on human erythrocytes and cardiac membranes from guinea pigs and rats. Recognized nucleoside transport inhibitors had high affinity (<50 nM) for NBMPR recognition sites associated with the nucleoside transporter complex in human erythrocytes, whereas calcium channel inhibitors and benzodiazepines had predominantly low affinity (> 1 μM). Although some recognized transport inhibitors, such as dipyridamole, show marked differences in affinity for NBMPR sites in guinea pig and rat tissues, benzodiazepines and calcium channel blockers displayed no such species selectivity and had low affinity (> 1 μM) for NBMPR sites in both guinea pig and rat cardiac membranes. Consequently, it is unlikely that agents such as benzodiazepines and calcium channel inhibitors cause significant inhibition of adenosine transport, and hence potentiate adenosine actions, at the concentrations required to induce effects through occupation of their respective, specific high-affinity sites.

Nucleoside transport inhibitors, dipyridamole and p-nitrobenzylthioinosine, selectively potentiate the antitumor activity of NB1011

2002 ◽  
Vol 13 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Christopher R Boyer ◽  
Patricia L Karjian ◽  
Geoffrey M Wahl ◽  
Mark Pegram ◽  
Saskia TC Neuteboom
Keyword(s):  
Antitumor Activity ◽  
Nucleoside Transport ◽  
Nucleoside Transport Inhibitors ◽  
Transport Inhibitors

Steroid hormones are novel nucleoside transport inhibitors by competition with nucleosides for their transporters

2014 ◽  
Vol 443 (2) ◽  
pp. 505-510 ◽  
Author(s):  
Masahiro Kaneko ◽  
Fumihiko Hakuno ◽  
Hiroyasu Kamei ◽  
Daisuke Yamanaka ◽  
Kazuhiro Chida ◽  
...  
Keyword(s):  
Steroid Hormones ◽  
Nucleoside Transport ◽  
Nucleoside Transport Inhibitors ◽  
Transport Inhibitors

Heterogeneity of high affinity nitrobenzylthioinosine binding sites in mammalian cortical membranes: multiple forms of central nervous system nucleoside transporters?

1984 ◽  
Vol 62 (8) ◽  
pp. 961-963 ◽  
Author(s):  
James R. Hammond ◽  
Alexander S. Clanachan
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Guinea Pig ◽  
Binding Sites ◽  
Specific Binding ◽  
Mammalian Species ◽  
Nucleoside Transport ◽  
Single Class ◽  
The Central Nervous System ◽  
Cortical Membranes

Specific binding of [3H]nitrobenzylthioinosine to cortical membranes from several mammalian species was investigated. Rat, mouse, guinea pig, and dog membranes contained an apparent single class of binding sites; there was, however, a marked species-dependent variation in their affinity for [3H]nitrobenzylthioinosine. Rabbit cortical membranes contained two classes of binding sites and the high and low affinity components were similar to those found in guinea pig and dog cortical membranes, respectively. The [3H]nkrobenzylthioinosine binding sites in rat and the low affinity sites in rabbit were atypical in that they exhibited a low affinity for dipyridamole. It is proposed that these latter sites may represent a form of the central nervous system nucleoside transport system which is less susceptible to inhibition by dipyridamole.

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