In this study, we examined suitable conditions for tissue fixation with
methacarn and
ethanol dehydration and storage of
paraffin-embedded tissues (PETs) on gene expression analysis. With fixation and
dehydration of rat liver tissues for up to 16 h (overnight) and 1 week, respectively, at 4 degrees C, integrity of extracted total RNAs and
polypeptides did not vary, the former integrity being constantly lower than that with unfixed frozen tissue, while
protein yield was slightly reduced with increasing
dehydration. Retained expression levels of mRNAs and
proteins were mostly unaffected by the period of fixation but slightly fluctuated with the length of
dehydration. When PETs were stored for up to 12 months, integrity of both total RNAs and
polypeptides was retained at 4 degrees C but reduced at room temperature. Reduced expression levels of mRNAs and
proteins were also noted by storage at room temperature after 12 and 3 months, respectively. However, neither tissue processing nor storage affected variability in either
mRNA or
protein levels among samples. Thus, the results suggest that, for gene expression analysis, tissues can be fixed with
methacarn and dehydrated for at least 1 day and 1 week, respectively, and PETs can be stored for at least 12 months, but a temperature of 4 degrees C is preferable.