Ultrastructural characteristics of untransfected control and hERG transfected CHO cells. CHO hERG or untransfected cells from 37°C were split and kept subconfluent for 3 d at 30°C or 27°C. At 30°C, hERG transfected CHO cells showed numerous large vesicle/vacuole-like structures (A,B), which were fewer in number in untransfected 30°C CHO cells (B). At 27°C, the number of vesicle/vacuole-like structures were reduced compared to the 30°C cells (C,D cf/A,B). Immunolocalized hERG + 5 and 10 nm colloidal gold secondary antibody was present on vesicle/vacuole-type membrane (E,F, respectively). hERG + 10 nm colloidal gold secondary labelling was present adjacent to golgi (F). cm, cell membrane; gl, golgi; nu, nucleus. Bar, A-D,5 μm. E,F, 250 nm. E inset, 100 nm.