Figure 1.

a Apoptotic PARP cleavage was inhibited by acidic solutions in Xenopus egg extracts. Interphase egg extracts in the absence or presence of 10 mM AA, 10 mM DHA, and 10 mM Ac were incubated at room temperature for indicated hours. Apoptotic cleavage of endogenous PARP was detected by western blot. Full length form (FL) and N‐terminal fragment (Frg.) are indicated by arrowheads. The pH values of egg extracts are also indicated at the bottom. b Apoptotic activation of endogenous caspases was inhibited by acidic solutions in Xenopus egg extracts. Interphase egg extracts were similarly treated as in a, and caspase activities hydrolyzing Ac‐DEVD‐pNA were measured. Data are presented as means ± SEM (N = 4). Open circle control, closed circle AA, open square DHA, and closed square Ac. c Spontaneous release of cytochrome c from mitochondria was not inhibited by acidic solutions in Xenopus egg extracts. Interphase egg extracts were similarly treated as in a, followed by centrifugation through a filter with 0.1 µm pore size. Equal amounts of protein were loaded for each lane and subjected to western blot against cytochrome c (Cyt. c) and actin (Actin)