Retinal [125I]iodomelatonin binding sites in the tree shrew (Tupaiidae)

The characteristics of melatonin-binding sites labelled by [125I]iodomelatonin in membrane preparations from the tree shrew retina were determined. Specific binding of [125I]iodomelatonin to the membrane preparations of tree shrew retina was rapid, stable, saturable, and reversible. Among the indoles tested only 6-chloromelatonin, melatonin and N-acetylserotonin had significant affinities to the [125I]iodomelatonin binding site. Scatchard analysis of the membrane preparations revealed a dissociation constant (Kd) of 51.0 +/- 16 pM and a total number of binding sites (Bmax) of 1.97 +/- 0.6 fmol/mg protein.