d-[ 3H]galactose incorporation into glycogen in retinal cone cells

Previous studies have shown that bovine retinas incubated with [ 3H]galactose incorporated it, unmodified, into large molecules. Light and electron microscope autoradiography showed a significant proportion of the label to be in cone inner segments, and pulse-chase studies showed it was subsequently transported to the synaptic pedicles. In this report, evidence is presented to show that the galactose-labelled macromolecules are resistant to hydrolysis by proteolytic enzymes, testicular hyaluronidase, chondroitinase ABC, β-glucosidase and β-glucuronidase, but are readily degraded by α-amylase and β-galactosidase, and to a lesser extent by β-amylase. Treatment with α-amylase also leads to specific removal of radioactivity from cone inner segments and pedicles, as judged by light-microscopic autoradiography. These studies appear to indicate that the cone-specific galactose label is in glycogen or glycogen-like molecules.