Abstract
A DNA-dependent fluorescence enhancement assay using the dye Hoechst 33258 was developed to quantitate cell number in crude detergent lysates of cells. The assay, which uses a simple filter fluorometer, is sensitive enough to measure 1 x 10(4) cells without interference from mercaptans, culture media, and protein solutions. They assay can be done with freeze-thawed lysates. Fluorescence intensity values are linearly related to cell number in the range of 1 x 10(4) to 2.5 x 10(5) cells for L-929, BHK, and CHO-Kl cell lines.