Binding sites of peanut agglutinin in mammalian retina

Histochemical studies were carried out of the binding sites of a lectin, peanut agglutinin (PNA), in the mammalian retina, using lectin labeled with either fluorescein or horseradish peroxidase. In all mammalian species examined, monkey, pig, cat and rabbit, the cones were intensely labeled with the lectin but the rods were unlabeled. The cone synaptic pedicles, the inner synaptic layer, the internal limiting membrane and the retinal vessels were also labeled. It is suggested from the specificity of the PNA binding that galactosyl and/or galactosaminyl residues are present in the mammalian cones, but not in the rods.