INTERACTION OF PLASMA PHOSPHATE WITH THE PHOSPHORUS COMPOUNDS 479^ 



In what follows we shall compare the rate of interpenetration of 

 labelled phophate ions into the corpuscles with that of labelled hexose- 

 monophosphate molecules. As the latter are easily decomposed in the 

 plasma, we have first to discuss the behaviour of the hexose-mono- 

 phosphate in this medium. 



RATE OF DECOMPOSITION OF HEXOSE-MONOPHOSPHATE 



The usual method applied to the study of the decomposition of hexose- 

 monophosphate under the action of enzymes is the determination of 

 the amount of phosphate ions split off in the course of the experiment. 

 This is a highly satisfactory method if, at the start of the experiment,, 

 no appreciable amount of inorganic phosphate is present. It is not very 

 satisfactory, however, if the decomposition of a slight amount of phos- 

 phorus ester is to be determined in the presence of large amounts of 

 inorganic phosphate. In such a case the use of labelled hexose-mono- 

 phosphate and the determination of the amount of radioactive phosphate 

 split off is much to be preferred to the first mentioned method. Even 

 large amounts of inorganic phosphate present at the start of the experi- 

 ment will in no way influence the results as these are, in contrary to 

 the phosphate split off from the labelled phosphorus ester, not radio- 

 active, and thus not recorded by activity measurements. 



In our experiments we have shaken 10 cc. of rabbits' blood for a few- 

 hours in a thermostat, after the addition of labelled hexosemono- 

 phosphate containing about ^15 mgm P. The hexosemonophosphate 

 (Embden ester) was prepared by Dr Ostern and kindly presented us 

 by Professor Parnas. At the end of the experiment the activity of the 

 total acid-soluble P of the corpuscles, that of the organic acid-soluble P 

 of the plasma, and also that of the inorganic phosphate present in the 

 plasma was determined. The results obtained are seen in Table 3. 



The first two samples were shaken in air after the addition of oxalate, 

 the four latter samples in a mixture of COg and Og after addition of 



Table 3. — Hydrolysis of Labelled Hexosemonophosphate 

 Added to Blood in vitro at 37° 



