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 (KD) of about 8·5 nm and a maximal number of binding sites (Bmax) 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.