Figure 4.

Immunohistochemical staining of ACE2 in human normal adrenal medulla and pheochromocytoma tissues. (A, B) were the serial sections of the same adrenal medulla. (C, D) were the serial sections of the same pheochromocytoma tissues. (A, C) showed Haematoxilin-Eosin (HE) staining. (B, D) were stained with antibodies aganist ACE2. Original magnification: ×100. Areas in black boxes in (A–D) were shown enlarged in (E–H) (×400), respectively. In the healthy adrenal tissues, c cells (pointed by black arrows) could only be distinguished in the adrenal medulla under high magnification (E, F), and exhibited no obvious ACE2 immunoreactivity. In sections obtained from pheochromocytoma tissues, ACE2 immunoreactivity was also not observed in pheochromocytoma cells (pointed by yellow arrows).