IN MIGRATING FIBROBLASTS, RECYCLING RECEPTORS ARE CONCENTRATED IN NARROW TUBULES IN THE PERICENTRIOLAR AREA, AND THEN ROUTED TO THE PLASMA-MEMBRANE OF THE LEADING LAMELLA

By following the intracellular processing of recycling transferrin rec eptors and the selective sorting of a-2 macroglobulin in chick embryo fibroblasts, we have shown that the concentration of 60 nm diam tubule s which surrounds the centrioles represents a distal compartment on th e recycling pathway. In migrating cells transferrin receptor tracers c an be loaded into this compartment and then chased to the cell surface . When they emerge the recycling transferrin receptors are distributed over the surface of the leading lamella.