Rod disc turnover in the dog

Tritiated l-leucine was injected intravitreally into normal adult dogs to study rod outer segment renewal. Eyes were removed at various times after injection and the retinas prepared for light microscope autoradiography. Rod outer segment disc turnover was found to be similar to other species, i.e., discs were produced at the base of the outer segments and migrated sclerad with time. The time for turnover averaged 6 days. Cone outer segments never showed banding of the labeled protein but rather a diffuse label such as reported in other species.