XTT assay

Dieter Palmer Dieter_Palmer at QM.AGRIC.WA.GOV.AU
Sun Oct 16 22:23:37 EST 1994

        Reply to:   RE>XTT assay
I regularly use the MTT assay for cell proliferation assays on sheep
lymphocytes. However, I have used the XTT assay for comparison. I followed the
paper by Roehm et al. (1991) An improved colorimetric assay for cell
proliferation and viability utilizing the tetrazolium salt XTT, J immunological
Methods 142, 257-265. XTT is used at 1 mg/ml dissolved in hot media and 25 ul
of this is added to each 100 ul of culture. I added PMS (phenazine
methosulfate) to the XTT solution (final concentration 25 uM). The XTT assay
works very well and gives a stronger positive signal than the MTT assay. The
reason why we don't use routinely is (apart from being a bit more time
consuming to prepare) that the non-lysed cells in the microwell plate can
interfere with the reading at 450 nm. Depending on the shaking time and the
number of cells in the well, the reading of your stimulated or unstimulated
cells varied. This is not a problem in the MTT assay because are the cells are
lysed. The advantage of the XTT assay obviously is that you can read the assay
over time without having to kill the cells.

Dieter Palmer

Date: 14/10/94 10:08 PM
To: Dieter Palmer
From: Geir Johannessen
Has anybody any experience with the XTT assay for counting living cells?
Preferably used in tissueculture plates. I need to know procedure and 

Geir Johannessen		* Phone : + 47 55 54 45 29
Laboratory for biotechnology	* Fax   : + 47 55 31 49 52
University of Bergen		* E-mail:mblgj at alf.uib.no
Norway				* http://www.uib.no/People/sub/Geir.html

More information about the Methods mailing list