Originally Communicated in Acta Physiol. Scand, 16, 20 (1948) 



46. NOTE ON THE INORGANIC PHOSPHATE 

 OF BLOOD PLASMA 



Grace de C. Elliot, L. Hahn and G. Hevesy 



From the Institute for Research in Organic Chemistry, Stockholm. 



In tracer work with radiophosphorus, we often add labelled sodium 

 phosphate to blood plasma or inject it into the circulation and follow 

 by means of radioactive measurements the path of the tagged phosphate 

 into the red corpuscles, their passage through the capillary wall or other 

 phase boundaries. For this type of work it is of great importance to 

 know whether the inorganic phosphate, added or injected, shows the 

 same behaviour as the endogenous inorganic phosphate present in the 

 plasma. Should that not be the case, the calculation of the amount of 

 phosphate penetrating from the plasma into the red corpuscles, for 

 example, from the distribution date of the ^^p added and the inorganic 

 phosphate of the plasma would clearly lead to wrong results. To inves- 

 tigate if and to what extent added and endogenous inorganic phosphate 

 show a different behaviour, we added to heparinized human or cat plasma 

 a tracer dose of sodium phosphate of negligible weight and, after rotating 

 the plasma at 37° for 1 hour in a thermostat, we electrodialysed the plasma. 

 At intervals varying between 1 and 18 hours, we took samples and 

 determined by radioactive measurements and colorimetric determi- 

 nations, respectively, at what rate the added labelled phosphate and 

 the endogenous inorganic P, respectively, is removed from the plasma. 



EXPERIMENTAL 



The dialysator applied was of the Hahn — Tisehus (1943) type. As membrane 

 a thin sheet of cellophane was used. To 20 ml heparinized plasma an equal volume 

 of physiological sodium chloride solution containing about 10 y labelled phosphate 

 of 14 microcurie activity was added. To keep the salt content of the plasma at 

 constant level a diluted sodium chloride solution was added at intervals. Through 

 the electrode cells a borate buffer solution of pH 7.6 circulated. The potential 

 applied to the ice-cooled dialysator was 20 Volts; the current intensity amounted 

 to 30 milliamp. The inorganic phosphate was extracted from the plasma with 10% 

 trichloroacetic acid. We carried out extractions both at 0° and at 20°. Imperfect 

 extraction would not influence our results, as aliquots of the same extract were 

 applied to the radioactive measurements and to the colorimetric determinations. 



