Figure 2.

Bax permeability induced at lower ionic strength was not reversed by raising ionic strength. Mitochondrial suspensions were treated with 8 nM Bax and 120 nM tBid for 30 min at 30°C in either 10 mM or 90 mM KCl buffer. At the end of 30 min, the rate of cytochrome c oxidation by these mitochondria was determined. Simultaneously, the mitochondrial suspension incubated in 10 mM KCl buffer was centrifuged and mitochondrial pellet resuspended in 90 mM KCl buffer to raise the ionic strength. This suspension was incubated for 30 min at 30°C, and at the end of the incubation, the rate of cytochrome c oxidation was measured. To correct for any loss of mitochondria during centrifugation, control and lysed samples with equivalent amount of mitochondria were also treated in an identical manner and the pellet resuspended in 90 mM KCl buffer (control without Bax or tBid) or H₂O (lysed) and rates measured. The results are means ± SE of three experiments.