Expression levels of mRNAs for catecholamine biosynthetic enzymes as markers of acute response to contusion stress during the early postmortem period.

Various stresses can be followed by sudden unexpected deaths, and autopsies sometimes fail to identify pathological findings that determine the cause of death. Pathologists occasionally explain such deaths as being due to overstimulation of sympathoadrenal systems, but postmortem assessment of antemortem sympathoadrenal activity has not been established. An animal model of weight injuries was used to quantify sympathoadrenal response to contusion stress, which is common in forensic fields. A weight was dropped from a given height onto the right dorsal limb of each anesthetized rat, with a control group and three stress groups (n = 4, each): 1000 g-80 cm, 1000 g-40 cm, and 500 g-40 cm. To explore the postmortem changes, we also included ten groups comprised of control and 1000 g-80 cm groups, whose tissues were harvested during 12 hours after euthanasia. Real-time quantitative polymerase-chain reaction was performed to quantify relative expression levels of mRNAs for catecholamine biosynthetic enzymes in the adrenals and the anterocervical ganglia: tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT). The expression levels of all target mRNAs in the adrenals increased with the intensity of impact (TH, p < 0.0005; DBH and PNMT, p < 0.005), and particularly, TH mRNA level exhibited near-stepwise elevation (p < 0.05). In contrast, no significant differences were detected in the anterocervical ganglia. Moreover, these mRNA levels in the adrenals decreased with increasing postmortem interval length. Thus, TH mRNA level may be a good marker of sympathoadrenal response to contusion stress during the early postmortem period.