Section V. 1921 [37] Tr.\ns. R.S.C. 



Glycogen in the Heart and Skeletal Muscles in Starved and WeU-fed 



A nimals 



By J. j. R. MACLEOD, F.R.S.C, and D. J. Prexdergast 



(Read May Meeting, 1921) 



It is known that the heart muscle contains a relatively high 

 percentage of glycogen and that this substance is particularly abun- 

 dant in the conducting structures of the organ. (1) It is also known 

 that the percentage of glycogen in the heart remains at a high level 

 in diabetes whereas it diminishes considerably in skeletal muscles 

 in this disease. (2) These facts bear an interesting relationship 

 to the results recently obtained by one of us (J. J. R. M.), working in 

 association with L. G. Kilborn, concerning the distribution of glycogen 

 in the tissues of various marine animals. In these investigations it 

 was found that the primitive heart of the dog fish (Squakis sucklii) 

 contains much more glycogen than the skeletal muscles or even the 

 liver (3). 



It seemed of interest, therefore, to investigate the behaviour of 

 the glycogen in the heart and muscles of rabbits and dogs after 

 periods of starvation or feeding with carbohydrate-rich food, and we 

 offer the results in the present communication. 



Methods 



The observations were made partly on rabbits and partly on 

 dogs, the animals being either starved or fed with abundance of 

 carbohydrate-rich food (oats, carrots and maize for rabbits, dog 

 biscuit for dogs) for three or four days preceding that on which they 

 were killed. Water was allowed during the starvation period. The 

 animals were killed by stunning, immediately bled, and the tissues to 

 be examined removed as quickly as possible and placed on ice so as to 

 diminish post-mortem glycogenolysis in the interval during which 

 the necessary weighings were being made. Portions of the tissues 

 were then cut into thin slices which were repeatedly pressed between 

 several layers of filter paper until this no longer became stained b\' 

 blood, the slices being then weighed and dropped into 60 per cent. 

 KOH solution, the volume of which was equal to that of the weighed 

 tissue. For a strictly accurate determination of the glycogen content 

 of the tissue several sources of error are incurred by the above pro- 



—40 a 



