ASCORBATE-INDUCED LYSIS OF ISOLATED MITOCHONDRIA 



55 



ascorbate, but the concentrations required are considerably higher. In 

 addition, raising the concentration shortens the lag period. If there is a 

 high concentration which inhibits swelling it was not reached in these 

 experiments. Oxidized glutathione (GSSG) produces a slow steady swel- 

 ling, possibly the result of partial reduction. High concentrations of as- 

 corbate do prevent glutathione induced swelling. 



Ascorbate Ivsis is more difficult to produce as the concentration of the 

 mitochondrial suspension is increased, and unlike phosphate-induced 

 swelling, it is not seen at all in concentrated suspensions. While this could 

 result from rapid exhaustion of ascorbate or Oo, increasing ascorbate in 

 proportion to the mass of mitochondria and thorough oxygenation have 



0,5 



0.4 



0.3 



CONTROLS 



30 " 60 

 MINUTES 



Fig. 3. Absorbancy changes due to ascorbate lysis of mitochondria are pre- 

 vented as long as strict anaerobiosis is maintained. Admitting air after 50 min. 

 results in a typical effect of ascorbate. 



been only partly successful in more concentrated suspensions. Perhaps 

 trace metal binding by the greater mass of protein is involved. 



Ascorbate induced lysis of the mitochondria requires the presence of 

 some oxygen (Fig. 3). Strict anaerobiosis will prevent lysis for at least 

 2 hr. If air is admitted after i hr., lysis occurs in the usual characteristic 

 fashion, with the possible exception that the lag period may be a little 

 shorter. In this requirement for oxygen, ascorbate lysis resembles swelling 

 induced by phosphate and many other agents. While swelling with these 

 other agents has been demonstrated to be dependent on endogenous or 

 added substrate in nearly every case, this is not true for ascorbate. Ageing 

 or other treatments of mitochondria which deplete endogenous substrate 

 do not alter the response to ascorbate. Long-term ageing at o^ tends to 

 shorten the lag period. 



Because of the oxygen requirement, the effect of electron transport 



