INTERNALIZATION AND LYSOSOMAL ASSOCIATION OF [¹²⁵I] ANGIOTENSIN II IN NOREPINEPHRINE-CONTAINING CELLS OF THE RAT ADRENAL MEDULLA

Abstract

The morphological localization of [¹²⁵I] angiotensin II (All) in the rat adrenal medulla (AM) was studied by light- and electron-microscopic radioautography in vivo. With light microscopy the presence of binding sites for All in both norepinephrine-containing (NE) and epinephrine-containing (E) cells was confirmed. With electron microscopy, it was found that All binds to the cell surface of NE cells, is progressively internalized, and is associated with lysosomes and Golgi complex within 20 min, whereas in E cells All seems to be internalized earlier and recycled back to the cell surface within 5 min without any appreciable association with intracellular organelles. These results suggest different intracellular pathways for All in NE and E cells of the rat AM.