A common basis for inhibition of nucleoside transport by dipyridamole and nitrobenzylthioinosine

TLDR: The apparent competition with nitrobenzylthioinosine at the latter’s high-affinity binding sites suggests that dipyridamole and lidoflazine inhibit nucleoside transport by interaction with these sites.

Abstract: Transport of uridine by monolayer cultures of HeLa cells was inhibited by nitrobenzylthioinosine, dipyridamole, and lidoflazine. Biphasic concentration-effect curves were obtained for inhibition of nucleoside transport by nitrobenzylthioinosine, but not for inhibition by dipyridamole. Dipyridamole and lidoflazine interfered with high-affinity binding of [ 3 H]nitrobenzylthioinosine to HeLa cells in an apparently competitive fashion; values of 1, 30, and 300 nM were obtained for dissociation constants, respectively, for nitrobenzylthioinosine, dipyridamole, and lidoflazine. The apparent competition with nitrobenzylthioinosine at the latter’s high-affinity binding sites suggests that dipyridamole and lidoflazine inhibit nucleoside transport by interaction with these sites.