Heart and adipose tissues are need attention to isolate total RNA. Because both tissues are extremely abundant specific components, cytoskeletal proteins and fats, respectively. RNA tends to be lost with the abundant components. Specially heart structure are so strong due to their permanent function, continuing active movement throughout the life cycle. The suggestion I'm going to put is based on the isolation of cardiac cells from neonate pups (there are plenty of references!!!). I think you can get enough RNA if you repeat trials and errors with adult zebrafish too.

Make sure washing zebrafish bodies with DEPC-buffer several times. Even if you wash them enough, it may not be sufficient to get rid of all microbes, protozoa and other organisms originated from the fish tank. The microbial contamination is so different from the other animal like mice, the land land mammals. Remove several hearts and trim them the attached tissues in DEPC-buffer. Flush with enough DEPC-buffer through the aorta with  1 ml syringe fitted with 26 gauge needle to get rid or blood cells. Soak them in DEPC-buffer. Incubate the hearts at 28C for 2h in enough amount of collagenase types mix solution together after injecting the collagenase mix into the hearts. This will loosen the structure of hearts without damaging cells. Take the hearts and wash them similarly in the buffer several times. Transfer the the herats into a small Buchner flask containing enough trypsin-EDTA solution to isolate cells with a stir bar (flea) at low speed at room temperature. While you are seeing cloud in the solution, pour the suspended solution gently into collection tubes. Add more TE sol, stir and then repeat the procedure 3~4 times while avoiding the gluey aggregates that may inclued dissolved cytoskeletal proteins of damaged cells, ECM proteins and glycoconjugates, and plenty of DNA, too. Immediately make pellet of the collected cells and wash with the buffer at each collection. Pull all the collection together. This collected cell pellet is the your starting material for RNA isolation.

I hope you do succeed eventually by optimizing the procedure.

Keep the procedure in mind. I also found the protocols you may follow the methods.

J Vis Exp. 2010; (37): 1717.

Nature Protocol 8(4):800-9 · April 2013

J Vis Exp. 2014; (94): 52248.

Dear Mr. Sang Ho Lee,

Thank you so much for information. I will update after trying.

Hello

Yes , for work with zebrafish must be take the extreme precaution to prevent contamination and to acquire pure samples .

for protocols you can see these links , Good Luck

https://www.researchgate.net/post/How_can_you_extract_total_RNA_from_a_Zebrafish_Heart

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4729522/

well what  was the age of the zebrafish ...as the amount of RNA in organs could vary from the age to age i mean Hpf

Kindly check that and use the RNA isolation from zebrafish protocol available in JOVE . it is an online veido publication that shows you the procedures.

Hope this helps.

Best,

Ratish

Hi, all, I tried a few kits and get nice concentration of RNA from individual heart tissue.