ASCORBATE-INDUCED LYSIS OF ISOLATED MITOCHONDRIA 59 



well be the result of complexing with metals rather than reducing action, 

 for quinone is even more effective than hydroquinone. At 5 and 10 mM 

 hvdroquinone or quinone alone cause a small amount of swelling of the 

 phosphate type. 



The question whether ascorbate induced lysis of mitochondria is 

 dependent on entry of electrons into the electron transport chain cannot 

 be answered completely just now. It appears to be dependent on some 

 trace metal effect. For the moment we must keep in mind the fact that 

 CN, antimycin A, and SN 5949 may act as metal complexing agents as 

 well as electron transport chain inhibitors. 



0.5 



0.4 



0.3 



0.2 



0.1 



0.3mM ASCORBATE 

 (A 



10 20 30 



MINUTES 



Fig. 8. Comparison of nitrite, hydroquinone, and quinone with 15 mM 

 ascorbate as inhibitors of the lysis of mitochondria induced by 0-3 mM 

 ascorbate. 



The lytic action of low ascorbate concentrations is clearly established 

 as a different phenomenon by experiments in which ascorbate is added 

 after phosphate + substrate swelling is more or less complete. In Fig. 9 it 

 may be seen that the typical ascorbate type of optical density change curve 

 occurs after phosphate swelling. The lag is similar and the absorbancy 

 falls to very low values. This figure also illustrates the fact that the typical 

 lag period (usually shortened a little) occurs after the mitochondria have 

 been at 25" for 30 min. Similar results are obtained after 60 min. This 

 clearly indicates that ascorbate lysis is basically unchanged by ageing and 

 is not dependent on endogenous substrate. In Fig. 10 it may be seen that 

 the same inhibitors block ascorbate-induced lysis after phosphate swelling 

 has occurred as with fresh mitochondria. 



Because of the possibility that HoOo production was involved in the 

 metal-ascorbate induced lysis, the effects of catalase and of HoO.^ were 



