I agree with Michaela.

Also, you can manage the orientation of aorta in OCT embedded blocks. First solidify a thin layer (2-3 mm) of OCT in the mold using dry ice. Then place the aorta horizontally on the solidified layer. It will stick to the initial layer of OCT. Then add more OCT above the aorta and let it solidify on dry ice. 

Now you have aorta in single perfect orientation. By rotating the block on cryostat, you can have sagital and well as cross-sections.

Good luck!

i want to get lumen diameter, because some histological preparations not ggod circumference

i guess u should use  a cryostat for preparing the slides u will get a thin and fine lumen to measure the diameter. 

The rat aorta is very thin/fine. While embedding your aorta, make sure that you will be geting a perfect cross sections. You have very little control of the orrientation of frozen tissue. I would suggest working with FFPE tissue. After fixation and infiltration with paraffin your aorta will become hard and easy to embed few peeces in the same block. You can get a pretty good average from measuring the diameters on H&E stained slides. 

I agree with Michaela.

Also, you can manage the orientation of aorta in OCT embedded blocks. First solidify a thin layer (2-3 mm) of OCT in the mold using dry ice. Then place the aorta horizontally on the solidified layer. It will stick to the initial layer of OCT. Then add more OCT above the aorta and let it solidify on dry ice. 

Now you have aorta in single perfect orientation. By rotating the block on cryostat, you can have sagital and well as cross-sections.

Good luck!

Good idea Vijayendra! I do this all the time for paraffin embedding but never in O.C.T.

This should work! Thanks!