An improved DAPI-DNA cytofluorometry by hypotonic cytolysis. Its application to tumor cell heterogeneity.

The effect of cell cytolysis on DAPIDNA cytofluorometry was studied in order to eliminate nonspecific cytoplasmic hindrances in DAPI staining. A great improvement in the reproducibility of DNA determination was attained when cells were treated with hypotonic KC1 (0.075 M) solution. The DNA content per cell of the mgC5 clonal line (normal diploid cell containing 2C DNA units) after hypotonie treatment was 3.07 ± 0.06, while that of mgC5 cells without hypotonic treatment was 3.50 ± 0.26, indicating a remarkable decrease from 7.4% to 2.0% in the coefficient of variation.