Pathological observation of intramuscular hemorrhage after mechanical injury in rats

Objective To investigate the timedependent changes of intramuscular hemorrhage after mechanical injury in rats.Methods 56 SD rats were randomly divided into antemortem injury group(48 rats),postmortem injury group(4 rats),and the control group(4 rats).Antemortem injury group was sub-divided into 12 groups after establishment of mechanical injury model.Pathological changes of subcutaneous intramuscular hemorrhage were detected by HE and Prussian blue staining at different posttraumatic intervals.Results A large number of red blood cells,many neutrophilic granulocytes and a few mononuclear cells and lymphocytes could be seen in the injured area,and no brown-yellow granules were observed by Prussian blue staining from 6 h to 24th after injury.Red blood cells began to reduce in number,and inflammatory cell infiltration reached a peak at 2 d and 3 d post-injury.Granulation tissue began to come out,and a very small amount of brown-yellow granules could be seen at 3 d and 4 d with maximization from 6 d to 10 d after injury.A very small amount of bluestained hemosiderin was seen from 3 d after injury by Prussian blue staining.In postmortem injury group and control rats there were no changes as mentioned above.Conclusion The timedependent changes of subcutaneous intramuscular hemorrhage as detected by HE and Prussian blue staining may be helpful for estimation of wound age.