Hydrolysis optimum of TCA Feulgen reaction on lymphocytes, liver cells, and Ehrlich ascites tumour cells.

For simultaneous cytophotometric measurements of DNA and protein the Feulgen hydrolysis must be performed with trichloracetic acid (TCA) at room temperature because of the preservation of nuclear proteins. Already after 10 h of hydrolysis, a good discrimination between the frequency peaks in the histogram is obtained. The best results are achieved after a hydrolysis time in the range of the maximum of the hydrolysis curve (20 h). At this time, little variations of hydrolysis duration scarcely influence the cytophotometric data.