Originally published in Acta Physiol. Scand. 19, 370 (1950) 



35. TURNOVER OF PHOSPHATIDES 



Grace db C. Elliott and G. Hevesy 



From the Institute for Research in Organic Chemistry and the Laboratorj- of 

 Pharmacology of the Karolinska Institute, Stockholm 



Since the time when it was first shown that ^^p administered to animals 

 is easily incorporated into liver phosphatides (Artom et al., 1937; 

 Hahn and Hevesy, 1937; Perlman et al., 1937) and the first attempt 

 to arrive at a quantitative figure for the rate of renewal (turnover) 

 of liver phosphatides (Artom et al., 1938; Hevesy and Hahn, 1940 a), 

 the problem of phosphatide turnover in the animal organism has found 

 an ever-increasing interest. The above-mentioned observation was not 

 surprising in view of the early observation by Artom (1933) that iodi- 

 nated fatty acids, when administered, promptly enter the phosphatides 

 of the liver, of Sinclair's (1936) similar observation on feeding elaidic 

 acid, and the still earlier work by Ivanowics and Pick (1910) on the 

 change in iodine number of phosphatides extracted from the livers of 

 dogs after ingestion of cod li^'e^ oil. 



In later studies with ^^p^ liver phosphatides were found to be the 

 almost sole source of plasma phosphatides^-^ to interchange readily 

 between liver and plasma, and also to be metabolized to a large extent in 

 the liver. Furthermore, numerous investigations were carried out with 

 the aim to elucidate the effect on phosphatide formation by feeding 

 choline, cholesterol, amino acid, etc. Surveys of these investigations 

 were recently given by Chaikoff and Zilversmit (1948) and by Hevesy 

 (1948). 



PRECURSOR OF PHOSPHATIDE PHOSPHORUS 



The application of isotopic indicators in turnover studies often aims 

 at the determination of the average life-time of a type of molecules 

 in an organ. We wish, for example, to know the time during which the 



^1^ Artom et al. (1948) demonstrated recently that fed intact labelled phospha- 

 tide molecules can be absorbed into the circulation. These absorbed phosphatide 

 molecules were found, however, to account for a minor part only of the total 

 ainount of ^-P fed as phosphatide P. 



