MTT vs.3H Thymidine

Frederick Coffman fcsc at
Wed Aug 4 18:29:28 EST 1999

If you are interested in measuring DNA synthesis, incorporation of thymidine
is a direct measurement of that property.  The MTT assay is more an assay of
living vs. dead cells; more specifically it is an assay of cells with
functional mitochondria.  The yellow MTT substrate diffuses into the cells
and is reduced to a purple formazan product by mitochondrial dehydrogenases,
thus the amount of purple color in a well (of a 96 well plate) is directly
proportional to the number of living cells with functioning mitochondria. 
There are some caveats - cells undergoing apoptosis can show reduced
mitochondrial function hours before they would be classified as dead using
other assays, and in some conditions (like giving very low concentrations of
TNF to some tumor cell lines) cells show enhanced mitochondrial function wrt
this assay, but in general the MTT assay is a fairly reliable way to measure
cell death.

But if you're interested in DNA synthesis, by all means measure it directly.

In article <37a5be05.2333583 at>, skim7 at
(Pianoman) wrote:

>Hello Experts,
>In our lab, there is a little debate on the method and I wish anyone
>can give us idea.
>We are testing the effect of some reagents on cell proliferation and
>DNA synthesis.  We did some cell counting experiment using
>hemocytometer.  We are interested in DNA synthesis and  if possible,
>ribonucleotide reductase activity.
>At the point we did the experiment using hemocytometer, what is better
>method between MTT and 3H thymidine uptake?  Which one can we  draw
>more conclusion out of data with?
>I would really appreciate any kind of information.

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