EFFECTS OF THYROXINE AND RELATED COMPOUNDS ON LIVER MITOCHONDRIA 23 



TABLE YU— continued 



(b) Desaminot/iyroxirie 



ratios being roughly normal even in those cases where respiration was 

 partially inhibited. Added DPX was able to restore the inhibited respiration 

 and the restoration was as a rule complete in the case of thvroxine but most 

 often only partial in the case of desaminothyroxine. In the case of des- 

 aminothyroxine inhibition, the stimulation of the respiratory rate by DPN 

 was accompanied either by no change or by an increase in the rate of phos- 

 phate uptake. Most peculiarly, a somewhat different effect of DPN on 

 phosphorylation was obtained in the presence of thyroxine. In this case the 

 increased respiratory rate was never followed by an increase in phosphate 

 uptake and often it even resulted in a serious decrease of the latter, thus 

 giving the impression of a true uncoupling effect (Expts. la, 2a, 4a, 5a, 

 6a). Despite great efforts it has not yet been possible to obtain this effect in 



