Ayman, basically there is no big problem with rat lungs. Excise them, I would advise to cut them before fixation, don't put the whole organ in formalin for even fixation. These rat lungs are easy to cut and do not bear many endogenous enzymes which might disturb immunohistochemisty. You can use a normal protocol for embedding. After cutting and deparaffinization you will need to use an appropriate target retrieval depending on the antigen you look at.

Thanks Torsten. So you don't think it's necessary to perfusion-fix the animals? Also, upon excision how do you preserve them prior to paraffin-embedding? Do you leave it in 10% formalin?

Hi Ayman,

we work with mouse lungs (should be to different) and I prefer to perfuse the lung itself with 4% PFA. To do this open the trachea and inject the PFA in into the trachea to inflate the lung.

This way the lung does not collapse and does not need a long fixing time. We then submerge the lung in 4% PFA over night at 4° prior to embedding.