Would I expect there to be a significant loss of bioactivity of E4 diluted in PBS and then frozen once before use? I would prefer to make a batch and then aliquot and store, as opposed to making it fresh each time which introduces greater variation.
Hi, In my experience the best way to store, any steroid, not just E2 is in ethanol at minus 20 oC in a glass tube. The ethanol will not freeze. I use 200 micromolar as my stock. Beware steroids have a tendency to absorb to plastic and polypropylene tubes so always use glass tubes, or else you may not get out what you put in! Hope that helps. Forbes
Hi, In my experience the best way to store, any steroid, not just E2 is in ethanol at minus 20 oC in a glass tube. The ethanol will not freeze. I use 200 micromolar as my stock. Beware steroids have a tendency to absorb to plastic and polypropylene tubes so always use glass tubes, or else you may not get out what you put in! Hope that helps. Forbes
Thanks Alexander. We would like to inject the solution into mouse pups and the ethanol confounds our experiment. I had wondered whether some BSA might help prevent loss to the plasticware and help stabilise the solution - would you agree ? We only need the solution to be stable for 3 weeks. We can certainly use glassware, thanks for the tip. B.
In my experience I can say that not all steroids are stable diluted in ethanol:
I diluted 18-OHcortisol in ethanol and divided in aliquots at-20. After one year the preparation has undergone an alteration visible in LC / MS / MS.Most probable there are other intermediate steroidogenesis that are not stables.I should like other experiences
If you decide to use BSA, make sure that it is steroid free. BSA can bind steroids as well as other lipophilic substances!
You can make a storage solution in mM range in ethanol and making aliquots in micro volume (to avoid using the same aliquot several times) and store at -20°C. The stock solution is stable for severals months without BSA. Then, for the working solution diluted in PBS, the contribution of ethanol should be negligible if the injected concentrations of estradiol are of the ranges of micro or nM.
I was wondering do any of you know how volatile solutions of steroids such as testosterone, estradiol or progesterone
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