Serum starving - when is it ok? - Questions about when to serum starve in an experiment (Jun/01/2011 )

I do a lot of tissue culture experiments, and lately have been wondering about when it's ok to do serum starvation.

Typically, I serum starve in cell proliferation assays for 24 hours before adding drugs/ligands and leave for 7 days.

But when it comes to transfections, they sometimes work better in the presence of serum. So what happens when I want to do a cell proliferation assay? Is it ok to carry out the transfection in serum-containing media, and then switch to serum free after 4-6 hours (when the transfection has "finished") and leave for 7 days? Or does this completely skip the point of serum starving?

I guess my overall question is: can you serum starve after you've treated/transfected cells, or is it really necessary to do it beforehand? And does this make any difference to an experiment?

Thanks

If you look at some literature some will say that serum starvation was done to syncrhonize the cells to the same cell cycle stage. What I generally find is that if you starve the cells prior to your treatment, it actually sensitize the cells to treatment and resulted in increased cytotoxicity. So I guess it depends on why you are doing the cytotoxicity assay. Would it be to find out the effect of transfection? If that is the case and transfection was working better with serum than I think you should not starve the cells after the transfection just to run the cytotoxicity assay.