Axonal Transport of the Ca2+-Dependent Protein Modulator of 3':5'-Cyclic-AMP Phosphodiesterase in the Rabbit Visual System

Water-soluble proteins were extracted from individual retinas, optic nerves, combined optic tracts and lateral geniculate bodies, and superior colliculi of rabbits at 1, 3, and 18 days after injection of [3H]leucine into the right eye. The Ca2+-dependent protein modulator of 3′:5′-cyclic-AMP phos-phodiesterase (calmodulin) was isolated from these samples by a two-step polyacrylamide gel electrophoresis procedure. An analysis of the radioactivity incorporated into the total soluble proteins and the calmodulin revealed that most of the calmodulin was axonally transported at a slow rate (2–4 mm/day) and represented about 0.45% of the total transported soluble protein.