Oxygenation and Oxidation 



These relationships of cytochrome c to oxygen consumption in 

 tissues {Table II) and to metabolism {Table III) naturally led to thyroxine, 

 which somehow regulates oxygen consumption and metabolic rate. 

 There was some pertinent, though scanty and inconclusive literature 

 in this field. S. R. Tipton 44 ' 45 had reported evidence for the influence 

 of the adrenal cortical hormones, particularly on cytochrome oxidase 

 activity. A. Tissieres 46 had studied the influence of the thyroid gland 

 on cytochrome c, but his results were confined to a single tissue, muscle, 

 and his analytical values for cytochrome c in the normal tissue 

 appeared unacceptably low. I am glad to state that Tissieres (now 

 working in Professor Keilin's laboratory) has now informed me that 

 he has more recently 47 applied our technique 9 and has obtained much 

 higher values for muscle cytochrome c. To be of conclusive significance, 

 a hormonal effect upon cytochrome c, contained in all aerobic cells, 

 must be demonstrated for all tissues. Table IV is a summary of mean 

 values 11,48 for the concentration of cytochrome c in liver, kidney, heart 

 and skeletal muscle in groups of rats, subjected to thyroidectomy, 

 thiouracil thyrotoxicosis, and acute hyperthyroidism induced by in- 

 jection of thyroxine, in comparison with normal controls. After both 

 thyroidectomy and thiouracil there was a marked reduction in total 

 body cytochrome c, reflected in statistically significant decreases 

 {Table IV) in the cytochrome c concentration (and content) of all the 

 tissues examined. After the administration of thyroxine conclusive 

 results in the opposite direction were obtained. 



These data consistently support the view of a relationship of thyroid 

 function to cytochrome c concentration in tissues, and permit a tentative 

 thesis : Thyroxine exerts its effect through the agency of cytochrome c. 



Table II. Proportionality of Cytochrome c Concentration** 40 ' 43 and 

 Oxygen Consumption {Oxidase Activity) in the Tissues of the Rat 



* /il of 2 consumed per mg of dry weight of tissue per hour ; approximate magnitudes, 

 t y or /tgm of cytochrome c per gm of dry weight of tissue. 



H— 4 



49 



