3.25 in. x 4 in. Lantern Slides, Original Magnification: x31,000, and This study examined the intracellular secretory pathway for IgG using tritiated leucine to tag the protein backbone and tritiated galactose and glucosamine to tag the glycoprotein chains synthesized in the Golgi. EM autoradiography was used to follow the travels of IgG after synthesis. The results indicated that IgG (the major protein synthesized by these myeloma cells) moved from the RER to the Golgi for sugar addition to IgG and likely reached the cell surface via small smooth surfaced transport vesicles. Previously it had been suggested that IgG moved in soluble form through the cytoplasm and was secreted directly through the plasma membrane. No evidence was obtained for temporary storage in secretory granules.
