In my experiment, I use a HepG2 cell line for a cytotoxicity assay with Alamar Blue dye, to test toxicities of different metal ions on the liver cells. HepG2 is a liver carcinoma cell line from a Homo Sapiens (human) origin. I know that usually liver cell is used for cytotoxicity assay, however, I wonder what will happen if I use brain cell line instead? And what if I use rat cells instead of human cells? I noticed a study comparing a mouse neuroblastoma line (neuro-2a) to primary neurons found that neuro-2a cells were much less sensitive to neurotoxins, possibly due to a lack of important membrane receptors and ion channels. It means that some neuronal cell lines produce undesirable unrepresentative results. Also, neuronal cells are usually used for investigation of neurotoxicity but not toxicity to human via normal routes of toxic substance intake and degradation, i.e. detoxification in liver. Nonetheless, does it mean the results produced by neuronal cell line will be very different compared with by HepG2?
If I use rats instead of human liver cell line, I think the results will be similar but the dose used to produce the same response level may be lower because rats are much smaller in size than human? Am I right?