Development of a cryosection EM autoradiography technique and its application for the subcellular localization of receptors
Recent progress in immunocytochemistry and cryo-techniques has made it possible to study receptor localization at the subcellular level. For many receptor-ligand systems suitable antibodies are not available and it would be more appropriate to use radioligands to study these receptors. Although fresh frozen sections have been widely used in light microscopy (LM) autoradiography studies, to our knowledge, no one has established a technique using electron microscope (EM) autoradiography with ultrathin frozen sections.Unlike conventional EM approaches which can extract many biological molecules during dehydration and plastic embedding steps, we have adopted the method of Tokuyasu combined with LM autoradiography protocol for frozen sections to develop a new EM autoradiography technique using ultrathin frozen sections. Heart blocks were fixed in 2% periodate-lysine-paraformaldehyde (PLP) and 0.1% glutaraldehyde (GA), sucrose infused, and frozen in liquid nitrogen. They were sectioned in a Reichert Ultracut S cryo-microtome equipped with a Reichert FCS cryo-unit.