410 ADVENTURES IN RADIOISOTOPE RESEARCH 



The animals were killed at definite times. 



The same organs in the same group were combined and frozen in 

 solid COg. 



A small amount of them were immediately dried at 70° and measured 

 as total tissue. 



The ground organs were then extracted with a lioiling mixture of 

 ether-alcohol 1/3 for 3 hr. The filtrate obtained was evaporated and the 

 residue extracted with petroleum-ether. 



The total fats obtained by evaporation of the petroleum-ether were 

 purified following the procedure of Folch and Van Slyke (9). 



The determination of the radioactivity was carried out with a Geiger- 

 Miiller counter. The activity of the samples was determined without 

 converting these into barium carbonate. 



RESULTS AND DISCUSSION 

 a) Liver 



The change in the relative specific activity of the total fat extracted 

 from the liver of control mice and mice injected with dinitro-cyclo- 

 pentylphenol with time is seen in Fig. 1(a). Each value indicates the 

 i*(J content of a fat sample obtained from 5 pooled livers. After admi- 

 nistration of labelled acetate, the incorporation of ^*C into fatty com- 

 ponents first increases, soon however due to the very rapid turnover rate 

 of a liver fatty fraction observed, the labelled fatty molecules will be 

 replaced by newly formed ones. As these molecules are formed from 

 a much less active medium — the specific activity of the liver acetate 

 rapidly decreases with time — they are less active than the degraded or 

 emigrated active fatty molecules. Due to these facts, the curve repre- 

 senting the change in the specific activity of the liver fat with time soon 

 shows a decreasing trend. This is found to be the case already after the 

 lapse of 7 — 15 min after the injection of labelled acetate. 



If the rate of fat formation is influenced by the effect of the adminis- 

 tered dinitro-cyclo-pentylphenol and accelerated in the first phase of the 

 experiments, more ^HJ can be expected to be incorporated into the fat 

 of the liver of such animals than in those of controls. The left part of the 

 curve will thus show a higher peak in the case of the mice treated with 

 the dinitro-compound than in that of the controls. The right part on the 

 curve on the other hand can be expected to show a steeper descent for 

 the animals injected with the dinitro-compound. tSuch a behaviour is 

 actually shown by the curves seen in Fig. 1 and also in those of Fig. 2 in 

 which the change of the specific activity of the exhaled CO2 is plotted 

 against time, after injection of labelled acetate and succinate. Succinate 



