370 ADVENTURES IN RADIOISOTOPE RESEARCH 



present in the extract was precipitated as ammonium magnesium phos- 

 phate. The filtrate obtained was then hydrolysed with 1 n HgSO^ for 7 

 min at 100° to split off the labile P which was then precipitated as ammo- 

 nium magnesium salt. The filtrate obtained after the last mentioned 

 operation was hydrolysed 100 min to split off the phosphate radical 

 of the hexosephosphate present. In order to avoid several consecutive 

 precipitations of ammonium magnesium phosphate which lead to an 

 accumulation of very appreciable amounts of ammonium salt in the 

 soluble fraction, we usually divided the filtrate obtained after precipi- 

 tation of the inorganic phosphate present as such in the tissue into 

 aliquot parts. One aliquot part was hydrolysed for 7 min, the phosphate 

 split off was precipitated, and the filtrate obtained was hydrolysed 

 for 100 min. Another aliquot part was hydrolysed for 7 min, the filtrate 

 obtained was hydrolysed for 12 hours, and so on. The phosphate of the 

 creatinephosphoric acid was split off by heating the solution for 30 min 

 to 40°. In some cases, the total acid soluble organic P w^as converted 

 into phosphate and Mas investigated in toto. The ammonium magnesium 

 phosphate precipitates obtained were dissolved in diluted hydrochloric 

 acid and an aliquot part was used for a colorimetric P determination. 

 To another aliquot part about 80 mgm non-active sodium phosphate 

 was added ; the total P present in the solution was then precipitated 

 as ammonium magnesium salt. The radioactivity of these precipitates 

 was determined by the aid of a Geiger counter. 



Though the separation of the different acid soluble P compounds 

 described above is far from being quantitative, it sufficed in most cases 

 for our purpose. 



In the experiments with blood, as anti-coagulent, ammonium oxalate 

 was used. The corpuscles w^ere centrifuged off and washed twice with 

 a physiological sodium chloride solution. In experiments in vitro, the 

 blood was kept in a COg— O2 atmosphere and was shaken, after addition 

 of labelled sodium phosphate of negligible weight, for 30 — 190 min 

 in a thermostat at 37°. 



RATE OF NEW- FORMATION 



As labelled phosphorus atoms can only be incorporated into organic 

 molecules in the course of a synthetic process, the radioactivity of the 

 organic phosphorus compounds isolated from an organ is a measure 

 of the rate of its total or partial resynthesis. It is, however, not permitted 

 to compare the specific activity (activity per mgm P) of the hexose- 

 monophosphate extracted from the kidney and the muscle, for example, 

 and to conclude from the fact that the hexosemonophosphate extracted 

 from the kidney is much more active than that secured from the muscle, 



