Stereospecific [3H]naloxone binding associated with opiate receptors in bovine retina

Using the tritiated opiate antagonist [³H]naloxone, stereospecific opiate receptor binding was demonstrable in a bovine retina homogenate. Scatchard analysis of the saturation experiments revealed an apparent dissociation constant (K_D) of about 8·5 nm and a maximal number of binding sites (B_max) of about 0·24 pmol/mg protein. The properties of opiate receptor binding in bovine retina parallel those found in the rat brain. Agonist binding was altered by sodium ions. Subcellular distribution of stereospecific [³H]naloxone binding showed the highest density of binding sites in the P₁-fraction and high concentrations in the P₀- and P₂-fraction.