On the State of Calcium and Phosphate of the Blood

Abstract

The report by Smith and Sternberger 1 that in many of their ultrafiltration experiments the sum of the ultrafiltrate and concentrate calcium fell very considerably short of the serum calcium and that the difference was due to an adsorption of calcium by the collodion membranes, led us to undertake an investigation of the phenomenon. This loss is important in relation to the differentiation of the blood calcium into a diffusible and non-diffusible fraction by procedures such as the one of Greenberg and Gunther. 2

It was found that the loss from serum with only normal amounts of calcium is negligible and only when the serum calcium is very considerably augmented, either by “in vitro” or “in vivo” measures, does the amount of calcium taken up by the membrane become of importance. The significance of diffusible and non-diffusible calcium determined under the usual circumstances on fresh blood serum is in no way vitiated by this finding.

This is borne out by the experiment given in Table I, which is representative of our results. The table shows the changes produced in the blood of a dog injected arterially with 0.5 gm. CaCl₂. In the original control blood sample and after the calcium has dropped back to the range of the usual serum values, the calculated serum content from the ultrafiltrate and the concentrate analysis agrees as well with the determined values as could be expected. In the samples with high calcium the loss is considerable.

It was found, moreover, that under these conditions not only the calcium but phosphate also is taken up by the membranes, and what is of greater significance, the phosphate which normally is completely diffusible becomes in very considerable part non-diffusible. This effect can be more strikingly shown “in vitro” by augmenting serum with calcium. An experiment of this kind in which beef serum has been augmented with calcium chloride is shown in Table II.