The distribution of inorganic phosphate of the blood between plasma and cells

Abstract

Since Greenwald's work on the organic acid soluble phosphorus our knowledge of the various phosphorus compounds in the blood is steadily increasing and acquiring significance. The determination of the inorganic blood phosphate, however, has been very questionable, particularly in corpuscles, due to the ease with which the organic acid soluble phosphate is hydrolyzed. Any method which requires considerable time or in which the phosphate has to be precipitated, or in which the red cells are washed or otherwise manipulated, comes very gravely under suspicion of having allowed a significant amount of hydrolysis to take place.

When working only with plasma these precautions are not so necessary. Bloor's 1 figures for inorganic phosphate in the corpuscles are admittedly high. A method very well suited to estimation of inorganic phosphate is that of Bell and Doisy 2 in which the color of the blue reduction product of phosphomolybdic acid is measured as in Folin's uric acid and phenol determintion, the limiting factor, however, being the phosphate.

Our results have been briefly as follows:

When working rapidly with the Bell and Doisy method, the inorganic phosphate in the plasma and the whole blood is the same within the limit of error of the method. The few exceptions to this were traced to improper handling of the blood or too long a time elapsing before the determination. Even here the whole blood gave figures much lower than Bloor's. This shows that the phosphate ion in its relation to cells and plasma behaves differently from all the other ions studied in this respect. The chloride, for instance, is never present in cells and plasma in the same concentration. This exceptional role of the phosphate ion is, however, not so surprising when we consider the organic acid soluble phosphate, in a sense the counterpart of the chloride combined with protein.