Cytochrome crelease and caspase activation in hydrogen peroxide‐ and tributyltin‐induced apoptosis

The ability of H2O2and tributyltin (TBT) to trigger pro‐caspase activation via export of cytochrome cfrom mitochondria to the cytoplasm was investigated. Treatment of Jurkat T lymphocytes with H2O2resulted in the appearance of cytochrome cin the cytosol within 2 h. This was at least 1 h before caspase activation was observed. TBT caused cytochrome crelease already after 5 min, followed by caspase activation within 1 h. Measurement of mitochondrial membrane potential (ΔΨm) showed that both H2O2and TBT dissipated ΔΨm, but with different time courses. TBT caused a concomitant loss of ΔΨmand release of cytochrome c, whereas cytochrome crelease and caspase activation preceded any apparent ΔΨmloss in H2O2‐treated cells. Thus, our results suggest that different mechanisms are involved in triggering cytochrome crelease with these apoptosis‐inducing agents.