Degradation profile of mRNA in a dead rat body: basic semi-quantification study

To profile postmortem degradation of mRNA, total RNA was extracted, at given postmortem intervals, from the brain, lung, heart and liver of rats left at 20 degrees C. In electrophoretic analysis, total RNA was most stable in the brain, moderately stable in the lung and heart, and most unstable in the liver. Northern blot analysis of total RNA extracts from the brain and liver of dead rats with a cDNA probe for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) showed that GAPDH mRNA degraded in a similar fashion to total RNA. Analysis of the postmortem degradation profile of GAPDH mRNA with real-time reverse transcriptase-polymerase chain reaction (real-time RT-PCR) gave results consistent with those above, indicating that real-time RT-PCR is reliable for estimation of the mRNA level in specimens from dead bodies. Real-time RT-PCR analysis showed that degradation rates of three housekeeping genes, GAPDH, beta-actin and hypoxanthine guanine phosphoribosyltransferase, in the brains of dead rats were similar. The degradation rate of interleukin-1beta (IL-1beta) mRNA induced by intravenous injection of LPS to rats was higher than that of GAPDH mRNA in the lung. In real-time RT-PCR analysis using GAPDH mRNA as an internal standard, the detection level of IL-1beta mRNA decreased in the postmortem interval. However, enhanced expression of IL-1beta was detected for at least 3 days postmortem.