Transmission electron microscopy showing normal morphology of cytoplasm, cell organelles, and nuclei of HepG2 cells not treated with matrine (A), characteristic ultrastructural morphology of autophagy (B), double-membrane (C) and a large number of autophagic vacuoles (D) of HepG2 cells treated with matrine, and sharply decreased autophagic vacuoles (E) of HepG2 cells treated with combination of 3-MA and matrine (A, B, E, × 4000; C, D, × 8000). Arrowheads represent double-membrane, thick arrows represent autophagosomes, and thin arrows represent autolysosomes. Nu: Nucleus.