506 ADVEXTURES IN EADIOISOTOPE RESEARCH 



ACCUMULATION OF PHOSPHATE IN THE CORPUSCLES 



As already mentioned, the interchange of P atoms between plasma and 

 corpuscles is not restricted to the P atoms of the free phosphate present 

 in the corpuscles, in contrast to the accumulation of additional phosphate. 

 If we increase the phosphate concentration of the plasma we may expect 

 to obtain, after a sufficiently long time, a corresponding increase in the 

 free phosphate concentration of the corpuscles. The exact determination 

 of the free phosphate content of the corpuscles encounters some diffi- 

 culties, since even a slight decomposition of the large amounts of organic 

 phosphorus compounds present in the corpuscles during the separation 

 and extraction processes will appreciably influence the amount of free 

 phosphate found to be present in the corpuscles. This fact may be partly 

 or wholly the reason why such varying values are found for the inorganic 

 phosphate concentration of the corpuscles^^^ The average value found 

 for the free P content of the corpuscles amounts to about 1.5 mgm 

 per cent. Since rabbit blood is composed of about 2 parts of plasma 

 and 1 part of corpuscles and the corpuscles contain somewhat less than 

 - as much inorganic P as 1 gm plasma, we can expect from the phos- 

 phate added to the blood about Vj to penetrate into the corpuscles. 



We determined the increase in the phosphate concentration of the 

 corpuscles due to addition of phosphate to the plasma in the following 

 experiments. To 2 cc. samples of rabbit blood 0.04 cc. phosphate buffer 

 of physiological concentration was added. Half of the samples obtained 

 was centrifuged at once, while the other half was first shaken for 2.^ 

 hours in a O2— COg atmosphere at 37°. Both plasma samples obtained 

 were precipitated with 5 per cent trichloroacetic acid and the P content 

 of the filtrate obtained was determined by the method of Fiske and 

 SuBBAROW. The result obtained is seen in Table 11. 



Thus, 1.54 mgm per cent or 12.5 per cent of the plasma phosphate, 

 corresponding to 17.6 per cent of the excess phosphate added, left the 

 plasma for the corpuscles in the course oi 2\ hours. During the same 

 time, 35 per cent of the ^^p added to the plasma was found by radio- 

 active measurement to have penetrated into the corpuscles. 



As mentioned on p. 498, this difference may be interpreted in the 

 following way. 12.5 per cent of the phosphorus atoms present at the 

 start of the experiment in the plasma accumulated during the experi- 

 ment in the corpuscles, increasing the inorganic P content of the erythro- 

 cytes. Besides this accumulation, a replacement of a part of the inorganic 

 P and of the organic P of the corpuscles by plasma P (interchange) took 

 place as well. The percentage P atoms present at the start of the experi- 

 ment in the plasma, which reached the corpuscles at the end of the expe- 



(1) 



Comp. for example, L. Halpebn (1936). 



