[Qualitative and quantitative analysis of cytotoxicity phenomena produced in vitro by bleomycin on BHK-21 cells]

The toxic action of Bleomycin (BLM) upon in vitro cultured BHK-21 cells was studied in the stationary growth phase (100, 200 and 400 mcg/ml doses) and in the exponential phase (25, 50 and 100 mcg/ml doses) at 24, 48 and 72 hours. The mitosis frequency was evaluated, showing that a progressive inhibition as well as morphological cellular changes exist. Quantitative morphometric measurements of the nuclear and cytoplasmic areas were also performed (Microvideomat, Zeiss). With this experimental method BLM works in a two-step manner: the cellular group that resists the first aggression phase depends upon the dose. In the initial phases (0-48 hours) after therapy, nuclear damage appears which demonstrates the existence of a certain resistance to antibiotics by the surviving cells. Secondly, the increase in diploid and polynuclear cells is interpreted as an interference upon DNA synthesis. Segregation of nucleolar components and, at high doses, degenerative cytoplasmic phenomena have also been detected. An inversion of the nuclear-cytoplasmic volume rate occurs, depending on the dose. This is interpreted as a Bleomycin action upon the protein synthesis, specially at the nuclear level.