Membrane recycling after endocytosis of cationized ferritin in cultured rat hepatocytes.

Cultured hepatocytes from adult rat livers were incubated for various durations (2 to 120 min) with cationized ferritin (CF) to trace the fate of surface membrane. CF was taken up by endocytosis in clathrin-coated vesicles and was found within 15-60 min in endosomes and mainly in multivesicular bodies (MVB). Lysosomes exhibited but scanty labeling, and the marker was not found in Golgi cisternae even at the longer incubation time. Two main observations result from our ultrastructural study: smooth vesicles seem to pinch off from the MVB to move toward the cell surface; moreover, smooth or coated vesicles fuse with secretion vesicles and recycle back to the plasma membrane. The present data thus demonstrate in cultured hepatocytes, the existence of intracellular pathways of plasma membrane that short-cut the Golgi cisternae and the lysosomal compartment.