Karnovsky fixative

Solution

The stock solution for Karnovsky fixative is as follows:

• 2.0 g paraformaldehyde
• 25 ml distilled water
• 1M sodium hydroxide 2 to 4 drops
• 50% glutaraldehyde 5.0 ml
• 0.2M cacodylate buffer, pH 7.4, 20.0 ml

Mix the paraformaldehyde with 25 ml of distilled water in a 125 ml Erlenmeyer flask. Heat to 60 °C on a stir plate. When moisture forms on the sides of flask, add sodium hydroxide and stir until the solution clears. Cool solution under the faucet. Filter, add glutaraldehyde and 0.2M buffer, pH range 7.2 to 7.4.

Modified solutions

Karnovsky's fixative solution is often modified for specialized applications. For example, 2% paraformaldehyde, 2.5% glutaraldehyde in 0.1 Molar sodium phosphate buffer (pH 7.4) has been used to study the ultrastructure of renal pelvis fragments.

References

References

1. [http://library.med.utah.edu/WebPath/HISTHTML/MANUALS/KARNOV.PDF Karnovsky fixative]
2. (2015). "Ultrastructural evaluation of shrinkage artefacts induced by fixatives and embedding resins on osteocyte processes and pericellular space dimensions". [[Journal of Biomedical Materials Research]].
3. (2020). "Morphology of the fetal renal pelvis during the second trimester: Comparing genders". [[Journal of Pediatric Surgery]].