In Acute oral tox studies (OECD 423), histopathological examination carried out on those animals died during the experimental period. But if they died with in 24 hrs then histopathological examination should be carried or not ?
Dear Ravi Pant
As per OECD guideline, the animals died after 24 h are necropsied. The animals if in moribund stage are humanely killed. If there is any evidence of gross pathological change in necropsy or in organ weight it is recommended to do histomorphological changes.
Dear Ravi
I am fully agreed with Dr Kushal Kumar that as per OECD 423 guidelines we need to test the lower dose of chemical if any amimal dies. But as per point 29 in the guideline if any animal died after 24 h survival, the microscopic studies should be carried out to see the pathological changes due to death. These data may be useful for you in future studies of your research. Please see the enclosed OECD guideline no. 423.
Good luck.
Thanks Dr Kushal and Dr Yadu!
I have also discussed with some toxicology experts they told that as all the animals (died or terminally sacrificed if survived) will go through gross pathological examination. If there is any symptoms appears, then only we will need to go for histopathology examination.
OECD 423 indicates that animals are dosed by oral gavage. The comments made so far refer to death by toxicity. Nothing is mentioned about accidental death due to instillation of the test material into the lungs. This often cannot be determined by gross examination of the tissues and requires microscopic evaluation. If one is dealing with an accidental garage-related death, there should not be any relationship to dose unless the compound administered also causes local anesthesia to the laryngeal tissues permitting easy access of the garage apparatus into the respiratory tract. If deaths are garage procedure-related, acute lesions (hemorrhage, edema) should be seen in respiratory tissues. In addition, one would likely see similar acute lesions around the larynx, as dilation of the larynx is restricted because of the cartilaginous tissues intrinsic to that organ. Thus, laryngeal cross sections are worth examining in addition to sections through the stem bronchi and associated pulmonary tissues. I once examined rats from a study dosed with a compound considered highly toxic. Following histopathology of the tissues mentioned above, it turned out that the toxicity resided with technicians responsible for the gavage and not the compound. A repeat with well trained personnel eliminated the problem.
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