Cultured cells at constant pH?

[Dom Spinella]

Ian York writes:
> This is probably a simple question, but I don't know where to start
> looking.
> 
> I want to grow tissue culture cells at a range of constant pHs for several
> days. The pH doesn't have to be fabulously accurate, but I don't want it
> to start dropping dramatically as the cells become denser. I'd like to
> try a range of, oh, I don't know, let's say 6.3 - 7.3 or so. 
> 
> Are there media that will do this? Where can I find recipes?

Ian:

The problem with most culture media using the common CO2/bicarbonate
buffering system is that bicarb is a very weak buffer at physiological
pH.  A better choice is one of the Good buffers such as HEPES (at 10 -
20 mM) which is a much stronger buffer at this pH range.  See R. Ian
Freshney's "Culture of Animal Cells" for recipes (or just suplement your
standard media with 20 mM HEPES).  Good luck.

--D.G. Spinella