

THE METABOLISM OF CARBOHYDRATE 433 



pancreas together control the sugar content of the blood. There is 

 also evidence of a mutual retardation of action effected between the 

 thyroids and the pancreas. Thus, when the pancreas is removed, 

 there occurs an increased metabolism of protein and fat, which is 

 attributed to the unrestrained activity of the thyroid and supra- 

 renal glands. These conclusions, if substantiated, afford a striking 

 example of the mutual interdependence of the various internal secre- 

 tions of the body (see later, p. ,503). 



The fasting depancreatized animal continues to excrete sugar. 

 As regards the source of this sugar, it has been shown experimentally 

 that injection of such amino-acids increased its formation. The 

 sugar may therefore be derived from protein decomposition. 



The question of the formation of sugar from tissue protein has 

 also been investigated by comparing the amount of dextrose (D) 

 secreted in the urine with the amount of nitrogen (N) secreted as urea, 

 giving the so-called ~ ratio. When a depancreatized animal is fed 

 on protein freed from all traces of carbohydrate, both dextrose and 

 nitrogen are increased in the urine, but the ratio is not altered from 

 what it was during fasting, which shows that the dextrose and the 

 nitrogen of the urine have a common source. If all the non-nitrogenous 

 moiety of protein were used to form sugar, the ? ratio would be 

 about 7. This can be seen from the following calculation: Protein 

 contains on an average 52 per cent, of carbon and 17 per cent, of 

 nitrogen; urea, CON 2 H 4 , contains 20 per cent, of carbon and 51 per 

 cent, nitrogen. If 17 grammes of nitrogen derived from 100 grammes 

 of protein are excreted as urea, the latter accounts for 6^ grammes 

 of carbon. This leaves 52-6 = 45J grammes of carbon to be 

 accounted for. In the gramme-molecular weight of sugar, C 6 H 12 6 

 180 there are 72 grammes of carbon. Therefore, if 72 grammes of 

 carbon go to form 180 grammes of sugar, 45^ grammes of carbon 



180x45^ 

 will form - ^ 



= 180x 136 



3x72 

 = 113-3 grammes of sugar 



D 113-3 



* N~ T7 =/ 



In an animal suffering from pancreatic glycosuria, however, all 

 the carbon is not converted, a D : N of about 3 to 4 being maintained. 



Dextrose may also be formed from the glycerine moiety of fats. 

 It has been shown that in the - condition of pancreatic glycosuria 

 glycerine yields an increase of sugar in the urine. It is to be concluded, 

 then, that after extirpation or in certain diseased states of the pancreas 

 dextrose may appear in the urine, and this sugar may be derived 

 from carbohydrates, proteins, and fats. 



4. Phloridzin Glycosuria. Phloridzin is a glucoside obtained from 

 the root bark of cherry and apple trees. If it be injected intc an animal 

 glycosuria results. If it be injected into one renal artery, sugar 



28 



