Characterization of the postmortem biochemical changes and the electrogenic transepithelial ion currents in rat colon-as possible markers for determination of time of death

ABSTRACT

Many biochemical studies of the experimental postmortem interval estimation were carried out on tissues incubated in vitro after extirpation. Because the extirpation affects cell viability, we investigated the changes in cathepsin D [cat D], lactate dehydrogenase [LDH], acid phosphatase [AcP] and alkaline phosphatase [ALP] activities and nucleic acids [DNA and RNA] content in the colon tissues of male Wistar rats occurring postmortem in situ in relation to time passed since death. Also, the postmortem transepithelial ion currents elecited by forskolin stimulation of rat colon were examined. The results showed significant and transient increase in cat D, AcP and LDH activities as early as 1 hr after death compared to control group [0 hr]. They reached the peak at 3, 6 and 9 hrs postmortem, respectively, then began to decrease at 6, 9 and 24 hrs, respectively till reached below control values at 72 hrs postmortem. On the other hand, ALP activity and nucleic acids content showed significant and permanent reduction beginning after 1 and 9 hrs postmortem, respectively. The maximum reduction was noted at the end of experiment [72 hrs postmortem]. The obtained results revealed also that the addition of forskolin to the serosal side of stripped rat colon at 0, 3 and 6 hrs postmortem induced a dose-related elevation in the short circuit current [SCC]. Following the next times 9 and 24 hrs, there was an increase in Kd and a decrease in Jmax with failure of response after 24 hrs. In conclusion, our results revealed that cat D, AcP, ALP and LDH activities and electrogenic ion current response of the colon to forskolin are usuefull markers for estimating time after death within the postmortem interval of 1-24 hrs. However, the changes in the nucleic acids content were correlated with the time elapsed since death during postmortem period of 1-72 hrs and can be used to estimate longer times passing after death