^52 



ADVENTURES IX RADIOISOTOPE RESEARCH 



FORMER INVESTIGATIONS 



In the first investigations (Hevesy and Hahn, 1940) in which the 

 specific activity of the plasma inorganic P of the rabbit was kept con- 

 stant during an experiment lasting 4 hours, the percentage renewal 

 of the phosphatides with incorporation of intracellular orthophosphate 

 or an organic phosphate which comes into rapid exchange-equilibrium 

 with the intracellular orthophosphate, was found to be 16. In the experi- 

 ments by Hahn and Tyren (1946) the mean value of the specific acti- 

 vity of the intracellular orthophosphate P of the liver was not determined. 

 A comparison of the values obtained for rabbit and rat livers shows, 

 however, that phosphatides are turned over at an appreciably more 

 rapid rate in the liver of the rat. In experiments of 2 hours' duration, 

 Hevesy (1947) found a percentage renewal with incorporation of intra- 

 cellular orthophosphate of 7.6 per hour for phosphatides of the whole 

 liver tissue of the rat and a value of 4.5 only for the percentage renewal 



Table 1. — Calculation of Bollman et al.'.s Experimental 

 Data of the Turnover of Liver Phosphatides 



(^> If, instead of considering tlie Ivnown mean phospliatide specific activity during tlie experiment, we 

 ■consider V2 of tlie end value, 4.83 is obtained. 



of the phosphatides present in the cell nuclei. Bollman et al. 

 (1948) arrived at a figure of 5.3 for the percentage renewal of the liver 

 phosphatides in the course of 2 hours. These authors raise doubts as 

 to the applicability to their case of the method of calculating the turn- 

 over rate as outlined above (Hevesy and Hahn, 1940 a) and perform 

 their calculations by applying the method worked out by Zilversmit 

 ei al. (1943). That the discrepancy between the percentage turnover 

 of the liver phosphatides of the rat as found by Bollman et al. 

 and by the present authors is not due to a difference in the method 

 of calculating the experimental figures obtained, is demonstrated in 

 Table 1, in which the results of the evaluation of the experimental data 



