LIPIDS PRESENT IN MUSCLES 739 



three generations, phospholipid and especially cholesterol were increased 

 in the muscles of rats which had been strenuously exercised. Hypertrophy 

 also occurred in most cases. These data are interpreted as indicating that 

 the increased levels of phospholipid and cholesterol may to some extent 

 be inherited. Table 7 summarizes the data of the Bloor tests (page 740). 



(5) The Effect of Atrophy on Muscle Lipids 



Morgulis and collaborators 212 reported that, when nutritional dystrophy 

 was induced in rabbits, a marked increase in cholesterol resulted. An 

 increase in phospholipid content was also noted in skeletal muscle, but no 

 change in phospholipid occurred in cardiac muscle. The changes in lipid 

 content were most marked in the gastrocnemius muscle, and least marked 

 in the abdominal muscles. The rise in cholesterol occurred first, and was 

 followed by an increase in phospholipid, and finally in neutral fat. Under 

 conditions of muscular dystrophy, a rise in ester cholesterol was found; 

 proportions of cholesterol ester as high as 27% were noted in dystrophic 

 muscles, as compared with values of 4 to 8% in the muscles of normal ani- 

 mals. 



In the case of muscles undergoing atrophy, following denervation, 

 Humoller et al. 213 found that the lipids of the affected muscle were broken 

 down at a rate faster than they could be replenished. In muscles which 

 had been denervated for longer than three days, the total fat and phos- 

 pholipid content gradually increased. The total fat exceeded that of the 

 contralateral control muscles within fifteen days after the operation. In 

 contradistinction to the behavior of other lipids, cholesterol does not ex- 

 hibit the initial drop in the early phases of atrophy, but it begins to increase 

 in amount immediately after neurotomy. It is suggested that the meta- 

 bolic disturbances in the muscle resulting from nerve section may affect 

 the cholesterol in a different manner than they do the phospholipids and 

 total fat. 



(6) The Effect of Fasting on Muscle Lipids 



Although it is generally accepted that fat stored intermuscularly may 

 decrease during fasting, most workers have agreed with Terroine 214 that 



2 » S. Morgulis, V, M. Wilder, H. C. Spencer, and S. H. Eppstein, J. Biol. Chem., 124, 

 755-766 (1938). 



213 F. L. Humoller, D. Hatch, and A. R. Mclntyre, Am. J. Physiol, 169, 654-658 

 (1952). 



214 E. F. Terroine, Contribution a Ja connaissance de la physiologie des substances 

 grasses et lipoidiques, Masson, Paris, 1919; Ann. sci. not, Zool. [10], 4, 5-397 (1920), 



