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Doubling time / Cytotoxicity assay - (May/25/2009 )

Hi Guys,

Somewhat of a basic question about semantics, but could anyone tell me how a doubling time experiment (to examine the effect of a compound) would differ from a cytotoxicity assay (also examining the effect of a compound)? Are they not the same? Also are doubling time experiment and proliferation assay used interchangably?

Lastly, is it possible to calculate doubling time directly from the absorbances given in MTT/Alamar blue assays? It would seem that the absorbances should directly relate to cell concentrations, so could you just sub in the absorbances for cell concentration in a doubling time equation? Doubling time (hours) = ln2 / ((ln (A/A0)) / t)

Somewhat confused! :(



Doubling time and proliferation assays are essentially the same. The difference between cytotoxicity and proliferation, is that one is looking at cell death (i.e. time taken to kill a percentage of cells, determined off the remaining live cells) and the other is looking at how quickly a population grows. Both can use the same reagents as they both work off living cells, but inferring the death in cytotoxicity assays.

You could use the absorbances directly, so long as you stay inside the reference range of the assay system and know how the absorbance relates to cell number (is it curvi-linear, straight line, quadratic etc.?). It would probably pay to determine this for each cell line that you are using.