HEK (human embryonic kidney) and Huh7 (hepatocellular carcinoma-derived) [24] cells were cultured in Dulbecco's modified Eagle's medium (DMEM), supplemented with 10% (v/ v) foetal bovine serum, 2 mM essential amino acids, 1% (v/v) nonessential amino acids. HEK cells stably transfected with full length ACE2, designated HEK-ACE2 [49] , and those overexpressing the testicular form of ACE (tACE), HEK-tACE [56] , were cultured in the same conditions with the addition of G418 (0.5 mg/ml) to the medium. SHSY5Y cells were cultured in DMEM-F12 media [57] , and SHSY5Y cells overexpressing tACE, SHSY5Y-tACE cells, were a kind gift from Dr. C. Rushworth, and were cultured in DMEM-F12 supplemented with G418 (0.5 mg/ml).