الفهرس 
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Abstract
The postmortem interval (PMI) or time passed since death is a critical step in most homicide or un-witnessed death investigations (including hospital deaths). It remains one of the most challenging variables to quantify and establish, despite the large amount of research undertaken.
The present work aimed to compare between two methods used to estimate the postmortem interval. The comparison included the vitreous humor potassium level and the postmortem changes affecting the suprarenal gland. The studied changes were histopathological changes, counting the chromaffin cells and calculating the suprarenal medullary area.
The study was conducted on 50 Newzeland male rabbits. At the beginning of the study the rabbits were sacrificed by cervical dislocation then they were classified into 5 groups (I, II, III, IV, V) according to the PMI (0h, 6h, 12h, 18, 24h).
For each group, the left suprarenal gland was dissected and placed in 10% formalin. Then put in paraffin according to the standard procedures and stained by Hx&E for histopathological examination. The vitreous humor was aspirated from the left eye and stored for further spectroscopic assessment of the potassium level.
The data obtained were analyzed statistically using SPSS version (16.0).
Experimental study:
As regard the vitreous humor potassium level (mmol/L), there was significant statistical increase in the mean value of its level with increasing PMI.
There was also significant statistical increase in the mean value of chromaffin cell count (cell/µm2) with increasing PMI.
On the other hand, the suprarenal medullary area (µm2) there was significant statistical decrease in its mean value with increasing PMI.
Referring to correlation, the results showed positive correlation between the vitreous humor potassium level (mmol/L) and chromaffin cell count (cell/100µm2). On the other hand, the findings showed significant negative correlation between the vitreous humor potassium level (mmol/L) and the suprarenal medullary area (µm2) while, it showed significant positive correlation with the total chromaffin cell count.
In the present study histopathological examination showed normal maintained architecture of the suprarenal gland at both (group I) (group II) with well differentiated cortex and medulla. Most cells had hyperchromatic and eosinophilic abundant cytoplasm, most of the nuclei were completely hyper chromatic with normal intact blood vessels.
While, in (group III) the cellular outlines of ZG, ZF and ZR and the medulla were clear and the cytoplasm showed vacuolation, some of the nuclei were pyknotic,
On the other hand, at 18hours postmortem (group IV) and 24 hours postmortem (group V), the three zones of the cortex cannot be differentiated, the cellular outlines of the ZG, ZF and ZR and of the suprarenal medulla were completely absent and the nuclei were totally pyknotic with vacuolation of the cytoplasm.
Conclusion:
from the obtained results, it was found that each of the vitreous humor potassium level; the chromaffin cell count and suprarenal medullary area could be used for estimation of the postmortem interval. Using of the vitreous humor potassium level in combination with either the chromaffin cell count or suprarenal medullary area, the total chromaffin cell count give more accurate estimation of the postmortem interval.