I plan to administer subcutaneous injections of 20 mg/kg each mouse in a daily basis. I'm in need of a substance in which, once dissolved, corticosterone remains active and not susceptible to go bad even if kept in the refrigerator. All instructions I have found seem to be oriented to the use of already dissolved corticosterone.
Hi Danae,
You can dissolve corticosterone in 100% ethanol up to 10mM. This can then be diluted using something like sesame oil. I recommend heating while dissolving in ethanol. At 10mM in ethanol, corticosterone will not precipitate out of solution and can be stored for at least one month at -20C.
Alternatively, there is corticosterone HBC complex available: http://www.sigmaaldrich.com/catalog/product/sigma/c174?lang=en®ion=US
This can be dissolved in water/saline but note that the complex is 66.7mg of corticosterone/g.
Yes , you can also disolve it in sesame oil and centrifugate until disappear . it will not precipitate and can store for a month but it always better you make the same day of injection.
Thank you both for your help! I'll sure try your suggestions at the lab. However, I have yet another doubt: I've seen some people dissolve the ethanol mix in saline instead of seasame oil. Do you think this would work? Thanks again!
Hi Danae,
I never see people dissolve it on saline and ethanol,but for sesame oil I did it in research for my master and it worked very well for me. A lot of researchers did it. I was working with nandrolone.
I have had issue using just sesame oil and heat to fully dissolve corticosterone, likely this is concentration dependent. Using ethanol and heat to solubilize corticosterone followed by dilution with sesame oil has always worked. You can do similar with DMSO as the limit of corticosterone solubility is even greater.
This is very useful information, thanks! Andrew Bartlett, I'm trying the same protocol that you described aiming to a final concentration of 5% ethanol in saline (for ip injections - 3mg/Kg of corticosterone). This give me a high volume of injection in a 300g rat (~5 mL). Is this usual for corticosterone administration? Am I missing something?
Rafael,
I don't dilute corticosterone dissolved in ethanol or dmso with saline. If you are using saline, I would recommend the HBC complex but again note the manufacturer's instructions. 3mg/kg for a rat is a pretty common "high" dose. The volume you inject depends on the concentration of your stock. For example, if you saturated your ethanol (10mM) and dilute to 5% of stock (1/20) your final concentration is .5mM. 3mg/kg for a 300g (.3kg) rat is .3kg*3mg/kg = .9 mg / rat. 0.5mM (0.0005M) is equivalently 0.0005*346.46g/L (the molecular weight of corticosterone, equivalently, 346.46mg/mL) = 0.17mg/ml and .9mg/.17mg/ml is 5.2ml. This is a really large injection volume. I would consider either using DMSO which has a solubility of 100mM, using Corticosterone HBC complex (which is soluble) or increase the concentration of your ethanol stock in the working solution. While some do dilute with saline or PBS, please note the attached product sheet which specifies max solubility of .5mg/ml for a 1:1 ethanol:PBS. Cheers!
That's great Andrew,
I got the same calculations, which is definitely a high volume. There is a lot of papers that use 3mg/Kg of cortiscoterone in 5% ethanol (final concetration in saline), but maybe they use the HBC complex (need to check this). I will try the dilution in DMSO and further dilution in saline/PBS. Thanks a lot for the answer. Have a nice one!