Originally published in Kgl. Danske Vidcnskabeimes Selskab. Biologiske 



Meddelelmr. 15, 5 (1940) 



34. TURNOVER OF LECITHIN, CEPHALIN, 

 AND SPHINGOMYELIN 



G. Hevesy and L. Hahn 



From the Institute of Theoretical Physics and Institute of Physical Chemistry, 



University of Copenhagen 



Phosphatide molecules present in tlie body have been taken up with 

 the food or have been built up in the organism. A spectacular proof 

 of the synthesis of phosphatides in the body is given by the fact thai 

 ducks raised in diets containing phosphorus only in inorganic form laifl 

 85 — 195 eggs during the summer^i\ These eggs contained 200 — 400 gm 

 phosphatides (corresponding to 8 — 16 gm phosphatide P), and this very 

 appreciable amount was synthesised by the organs of the clucks. On the 

 other hand, phosphatides can enter the circulation from the intestine. 

 The amount of phosphatide which is daily led by the intestinal lymph 

 into the circulation of the rabbit^^^ on normal diet was calculated to be 

 about 50 mgm. This is only about 1/5 of the amount daily synthesised 

 in the liver (comp. p. 323); one must further consider that an 

 appreciable part of the above mentioned 50 mgm was synthesised in the 

 mucosa of the small intestine. Thus, the phosphatide molecules of the 

 organs will be only to a small extent obtained directly from the food, 

 the overwhelming majority being built up in the body. 



CONCEPT OF TURNOVER 



The ultimate aim of the investigation of the origin of Ww ])hosphatide 

 molecules present in the body is to be able to state in which form ihr 

 hydrogen, carbon, nitrogen, oxygen, and phosphorus atoms present 

 in the phosphatide molecules were taken up by llic body and in what 

 steps they were involved until ultimately incorporalcMl iiilo ))liosphatidc 

 molecules. This exacting task can hardly l)e solved at prcscnl , ;\.vn\ we 

 must content ourselves with the deteimination oC 1 he place and rale 

 of formation oflhe phosphatide^ iiiolcculcs in 1 he body IVoiii glycerol. 



(i)G. FiNGERLiNG, Biochem . Z. 38, 44S (l<)ll). 



(2)H. SiJLLMANN and W. ^^■ILBRA^•^T, Biochem. Z. 270, 52 (1934) 



