The NRB-AF12 and ER-Tr subcellular distribution patterns and co-localization rates were confirmed using other NRB-insensitive cells (i.e., HepG2, HSC-T6, and HeLa cells; Figures 4A–C), and using NRB-sensitive cells such as freshly isolated rat caudal artery myocytes (Figure 4D). Interestingly, in this latter cell type, both fluorescent compounds stained not only intracellular structures, but also the plasma membrane. Co-localization rates of NRB-AF12 and ER-Tr in HepG2, HSC-T6, HeLa and primary rat vascular smooth muscle cells is reported in Figure 4E as Pearson's coefficient. These results indicates that NRB-AF12 labels intracellular structures with a pattern of distribution that is apparently very similar to that of ER-Tr, and is not confined to ER.