Fig. 6. Cell death may be related to accumulation of extracellular histone H1. (A) C₂C₁₂ cells were induced to differentiate. The culture medium was changed every 2 days. LDH activity was quantified in conditioned media harvested on the indicated days and in cell extracts. Extracellular LDH (in the extracellular space) is expressed as a percentage of the total enzyme. The insert shows cumulative LDH release, calculated using the data in Fig. 6A. (B) Necrosis (dashed bars) and apoptosis (closed bars) were determined by specific ELISA assays. Data are expressed as the absorbance at 410 nm per ng of DNA. (C) Heparin-displaced proteins from intact cells and TX-100/KCl extracts from the corresponding cells were subjected to [³⁵S]heparin ligand blot assay. Densitometric analysis of heparin-displaced histone H1 is shown as the percentage of total histone H1. Data are plotted as a function of the differentiation period (days 0-6). Results correspond to the average and s.d. of two independent experiments.

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