Flow cytometry and biochemical analysis of DNA degradation characteristic of two types of cell death.

By flow cytometry it has been shown that in rat thymocytes dying upon gamma-irradiation the reduction in DNA content per cell occurs well before the increase in outer membrane permeability. In contrast, in irradiated Burkitt's lymphoma cells the disturbance of plasma membrane permeability precedes the decrease of DNA content. Genome degradation in dying thymocytes of irradiated or hydrocortisone-treated rats is accounted for by internucleosomal DNA fragmentation. Postirradiation DNA cleavage in the 3 investigated cell cultures is disorderly and is probably caused by the activation of hydrolases in dead cells.