I have been using water soluble estradiol for the cell proliferation assay in 5Y cell line. My questions are;
1. Can we store the stock solution of estradiol in plastic container (microfuge tube)?
2. Is the water soluble form confined to particular studies or cell lines only?
3. Is this form of estradiol capable of entering into the cells or it just binds with the membrane associated receptors?
Dear Rubina,
The water soluble form of estradiol (E2) is a formulation where the steroid is encapsulated in hydroxypropyl beta-cyclodextrin (HPCD). As a result of this formulation, it dissolves in aqueous solutions quite readily. However, there are some caveats to consider when using it:
Depending on your "endpoint", the vehicle (HPCD) can have its own effects. For example, when measuring certain cell signaling events (phosphorylation of specific kinases), HPCD can itself alter the phosphorylation state of certain kinases. So if you're planning an experiment with water soluble E2, I would recommend running a vehicle control (HPCD) in parallel with your "untreated control" and experimental groups (where you treat with the water soluble E2).
As for your specific questions, I would offer the following:
1) You can store a stock solution of E2 in a microfuge tube. However, just make sure you aren't too close to the solubility limits of the steroid when storing stock solutions of E2. If your question specifically pertains to the water soluble variety, my recommendation is to make the solution fresh.
2) With respect to this question, please note the caveat I stated above.
3) Yes, the water soluble form of E2 is capable of entering cells. This formulation does not render it cell membrane impermeable.
Note that the water soluble form of E2 is different from the bovine serum albumin (BSA)-tethered E2 (called, "E2-BSA", where multiple molecules of E2 are linked to a single molecule of BSA via a carboxymethyloxime linker). E2-BSA is thought to be membrane impermeable, so any effects of this compound have been interpreted as being initiated at the plasma membrane (potentially, by acting on a membrane-associated estrogen receptor). However, caveats should be considered when using this compound as well. For example, there may be "free" steroid that may "contaminate" the powder/crystalline form of "E2-BSA". It is not completely clear how stable the association of E2 is with BSA once in solution or once the E2-BSA solution is exposed to cells/tissue.
I hope this helps.
Meharvan Singh, PhD
Thank You very much Sir for providing all the information I needed about estradiol. This is really helpful.
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