In 'undifferentiated' PC12 cells, GERL is not segregated from the Golgi apparatus

The present study examines the endocytosis of conjugates of horseradish peroxidase (HRP) with ricin and wheat germ agglutinin (WGA) in rat adrenal pheochromocytoma cells (PC12 line) cultured in the absence of nerve growth factor (NGF). In these cells acid phosphatase (ACPase) activity is not confined to a single cisterna and vesicles at the transaspect (mature face) of the Golgi apparatus which correspond to GERL of cultured neurons, neuroblastoma and other cell types. But ACPase is found in several cisternae of the Golgi apparatus as well as in lysosomes. On the other hand, thiamine pyrophosphatase activity, is found in a typical location within two or three cisternae of the Golgi apparatus near its transaspect. Following adsorptive endocytosis of HRP-labelled lectins (ricin-HRP or WGA-HRP) into PC12 cells, a reaction product is seen in dense bodies as well as in small vesicles and tubules throughout the cytoplasm, at the periphery of large vacuoles, in smooth and coated vesicles and tubules near the Golgi apparatus and in anastomosing tubules. The cisternae of the Golgi apparatus are not involved in the endocytosis of lectin-HRP. We concluded that in PC12 cells grown without NGF, unlike the case of cultured neurons and neuroblastoma cells, GERL is not segregated from the Golgi apparatus by either ACPase cytochemistry, or by the functional criterion of endocytosis of lectin-HRP conjugates.