title: Cation regulation of guinea pig cardiac nitrobenzylthioinosine binding sites.
abstract: The effects of several ions on [3H]NBMPR specific binding were characterized in guinea pig cardiac membranes. Binding of [3H]NBMPR was enhanced by Mg2+ Ca2+, Na+ and K+ but inhibited by Mn2+, Cu2+ and Zn2+. The effects of Cu2+ and Zn2+ were observed in micromolar concentrations while the effects of the other cations were observed between 1 and 300 mM. The anions tested had no significant effect on the binding. Scatchard analyses of the [3H]NBMPR saturation equilibrium data showed that the enhancement by Na+ and Mg2+ was due to an increase in the number of binding sites number with no change in apparent affinity. The inhibition of the binding by Cu2+ and Zn2+ was due to a decrease in both the apparent affinity and the number of binding sites. The regulation by cations imply that [3H]NBMPR binding sites are physiological receptors that may be involved in postreceptor coupling.
mesh_terms: D000818:Animals; D000838:Anions / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects; D002412:Cations / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects; D008024:Ligands; D008297:Male; D013868:Thioinosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D000838:Anions; D002412:Cations; D007473:Ion Channels; D008024:Ligands; D013868:Thioinosine; C001789:4-nitrobenzylthioinosine