Trp holorepressor-trp operator interaction studied by protein distribution analysis

[3H] imipramine exhibits both saturable and high affinity binding sites in human lung with a maximal number of binding sites of 7.50 pmoles/mg protein and a dissociation constant of 1.74 nM. Displacement studies indicate that these sites can be considered as specific of imipramine, tricyclic compounds and also monoamine uptake inhibitors:fluoxetine and nisoxetine. Atypical antidepressants were inactive as ligands of main known receptors.