whether liver back up tissue stored in liquid nitrogen WITHOUT Trizol reagent (normally used for protein extraction) could be used for RNA extraction? Any one ever had encountered such case?
I don't know about liver, but in my experience storing cells and brain tissue in -80 (after snap-freezing in N2) for later RNA extraction is fine. I also routinely do this for protein extraction and it works fine.
I agree with Nadia,the dissected tissue immediately put in liquid nitrogen is fine for later RNA extraction. It is much better than the cells kept in liquid nitrogen after trypsinization.