738 VII. LIPID DISTRIBUTION IN SPECIFIC TISSUES 



For further information as to the changes in the muscle lipids of rats, as 

 related to age, see Tables 9 and 10 of Chapter VI. The cholesterol content 

 has been reported to be greater in the muscles of the calf than in the corres- 

 ponding muscles of the cow. 205 



(4) The Effect of Increased Metabolic Activity 

 and of Exercise on Muscle Lipids 



Pasternak and Page 206 reported that the injection of thyroxine markedly 

 increased the phospholipids of muscle, but not the cholesterol content. 

 This observation is difficult to correlate with the results of Onizawa, 207 who 

 noted that a decrease in muscle cholesterol occurred concomitantly with the 

 removal of the thyroid gland. 



The muscle is apparently responsive to increased activity in the form of 

 exercise, and reacts by changes in both phospholipids and cholesterol. 

 Not only the amount of lipids but also their character varies with the ex- 

 tent of exercise to which the muscle is subjected. Reed and her co- 

 workers 208 found that forced activity and voluntary nocturnal activity in- 

 creased the proportion of intermuscular lipids in rats. Bloor and Snider 197 

 also reported a correlation between the extent of activity of beef muscle 

 and its phospholipid content. The higher the degree of activity of the 

 muscle, the higher was the level of phospholipids. Embden and Lawac- 

 zeck 209 noted that the cholesterol content of the different muscles of the 

 normal rabbit varied with the activity of the muscle. 



In a further investigation of this problem, Bloor 210 found that the muscles 

 of active rats and pigeons generally presented higher phospholipid values 

 than did the corresponding muscles of inactive animals. In the case of 

 muscles from chickens which had suffered from "range paralysis," it was 

 found that the phospholipid was invariably low, and the cholesterol higher 

 than normal. The P:C ratios were as follows, as compared with normal 

 values (in parentheses): ventricle, 5(14); thigh, 6(16); pectoralis major, 

 5(8); gizzard, 1.1(4). Furthermore, in muscles from patients suffering 

 from muscular dystrophy, Bloor 210 noted P:C ratios varying from 1 to 8 

 instead of a normal value of 14. In later studies Bloor 211 found that, after 



205 K. Hotta, Z. physiol. Chem., 125, 220-228 (1923). 



206 L. Pasternak and I. H. Page, Biochem. Z., 274, 122-145 (1934). 



207 J. Onizawa, J. Biochem. (Japan), 10, 425-434 (1928-1929). 



208 L. L. Reed, F. Yamaguchi, W. E. Anderson, and L. B. Mendel, J. Biol. Chem., 87, 

 147-174 (1930). 



209 G. Embden and H. Lawaczeck, Z. physiol. Chem., 125, 199-209 (1923). 



210 W. R. Bloor, J. Biol. Chem., 119, 451-465 (1937). 



211 W. R. Bloor, /. Biol. Chem., 132, 77-82 (1940). 



