INTERACTION OF PLASMA PHOSPHATE WITH THE PHOSPHORUS COMPOUNDS 481 



UPTAKE OF HEXOSEMONOPHOSPHATE BY THE BLOOD CORPUSCLES 



We interpreted the i'ormation of active phosphorus esters found in 

 the corpuscles as due to an enzymatic exchange process inside the 

 corpuscles, (the number of ester molecules decomposed being presumably 

 replaced by an equal number of newly formed molecules) into which 

 some of the active inorganic phosphate added to the plasma penetrated. 

 An alternative explanation would be that active phosphorus ester 

 molecules are formed in the plasma, diffuse into the corpuscles and are 

 replaced, in experiments in vitro, by an equal number of non- active 

 molecules leaving the corpuscles. We can test the correctness of this 

 explanation for each compound by adding to the plasma the active 

 phosphorus ester and determining, after the lapse of few hours, the 

 activity of the phosphorus ester molecules and the inorganic phosphate 

 of the corpuscles. So far we only carried out such experiments with 

 active hexosemonophosphate, prepared by Dr. Ostern and presented 

 to us most kindly by Professor Parnas. Several of the other labelled 

 phosphorus ester compounds were also synthesized in the laboratory 

 of the latter. The result obtained by us is that, if hexosemonophosphate 

 molecules diffuse at all into the corpuscles, the rate of their penetration 

 must be much slower than that of the phosphate ions. We arrived at 

 this result by supposing that the amount of active P to be expected in 

 corpuscles after the lapse of a certain time is wholly due to the pene- 

 tration of active phosphate ions from the plasma into the corpuscles 

 and independent of the presence of active hexosemonophosphate in the 

 plasma. The next step is to compare the calculated values for the activity 

 of the corpuscles P with those found by. the experiment and to ascertain 

 if any difference is shown by the two values. Should that not be the 

 case, then we must conclude that the rate of penetration of the hexose- 

 monophosphate molecules into the plasma is negligible compared with 

 that of the phosphate ions. The amount of labelled P in the corpuscles 

 is zero at the start, i. e. after addition of active hexosemonophosphate 

 to the plasma, and increases with time as discussed on p. 477. As in the 

 course of the experiment only a small part of the active hexosemono- 

 phosphate is hydrolysed, we are entitled to make the simplifjdng assump- 

 tion that the increase of the specific activity of plasma inorganic P 

 takes place in a linear fashion. We also assume that the decrease of 

 the difference in the specific activities of plasma phosphate P and 

 corpuscle phosphate P with increasing time will also take place according 

 to a linear function'^i^ The average value (comp. 474) of the last mention- 

 ed difference will be 



i(Sp-Si) = 0.5Sp-0.9S, 



<'' Thi.s assumption though incorrect does not cause an appreciable error. 

 Slvesy 



