THE TRANSLATIONAL INHIBITOR CYCLOHEXIMIDE REPRESSES GROWTH-FACTOR DEPLETION-INDUCED APOPTOSIS IN AN ALB-SV40T TRANSGENIC RAT-LIVER CELL-LINE

A transgenic rat line carrying the alb-SV40A transgene has been descri bed by this laboratory. Several cell. lines have been established from the livers of two of these rats. One of these cell Lines, L37, exhibi ts a large nuclear/cytoplasmic ratio and a well-differentiated cytopla sm containing numerous organelles. When L37 cells are placed into cult ure medium lacking necessary growth factors, cellular proliferation co ntinues for 48 hours after medium change. Subsequent to the initial 48 hours, cells begin to shrink and lose contact with adjacent cells, ev entually sloughing off the culture plate surface, with most cell death s occurring between 48 and 96 hours after medium change. Microscopic e xamination of sloughing cells indicates they possess highly convoluted and blebbed plasma membranes, a morphological characteristic of apopt osis. Ultrastructural studies demonstrate the ubiquitous presence of a poptotic bodies, When DNA isolated from growth factor-depleted cells i s resolved on agarose gels, DNA fragmentation ladders are observed at times of maximum apoptotic change, Quantitative analysis of L37 cells between 48 and 96 hours after the removal of the culture medium shows that 59% +/- 2% of the cells undergo apoptosis. When cycloheximide, pu romycin, or actinomycin D is added to the L37 cultures, only cyclohexi mide is able to repress apoptosis, indicating that the mechanism of ap optosis in the L37 liver-derived cell line requires a cycloheximide-se nsitive translational event. The extremely high rate of apoptosis, tog ether with the maintenance of hepatocellular characteristics, indicate s the usefulness of this cell line as a model in which to study the me chanisms of hepatocellular apoptosis.