The Precipitation of Blood Calcium by Lead

The treatment of inoperable cancer by the intravenous injection of suspensions of lead has stimulated interest in the fate of this metal in the blood stream. The original metallic colloid of Bell (1) is very sensitive to oxygen, and by in vitro experiments Brooks (2) and Bischoff and Blatherwick (3) showed that there was little likelihood of any of the metallic lead reaching the cancer as such. Aub and Reznikoff (4) had shown that the phosphates and carbonates were the only two of nine constituents normally found in blood which would neutralize the damaging effect of ionic lead to red cells, the phosphate ions being many times as effective as the carbonate. Fairhall and Shaw (5) found that the lead deposited in bones in lead poisoning is present as phosphate and not as carbonate or albuminate, and from a critical study of the solubilities of lead carbonate, dilead phosphate, and trilead phosphate, concluded that trilead phosphate was the form in which lead was transported in the blood in lead poisoning. Bischoff (3, 6) prepared various colloidal suspensions of lead with the inorganic constituents of the blood and found from rabbit tests that colloidal metallic lead, ionic lead and lead hydroxide were about equally damaging to the red blood cells. The oxycarbonate was less damaging and the phosphate without effect. Ionic lead, buffered with serum or red blood cells containing sufficient inorganic phosphorus to convert all the lead to phosphate, was also found to be non-toxic. The colloidal phosphate prepared for the rabbit experiments was then tried clinically by Ullmann (7), Pulford (8), Soiland, Costolow, and Meland (9), and others, Brooks (2), experimenting with the Bell metallic colloid and ionic lead, found that when these substances were added to serum, the amount of phosphorus precipitated from the serum (determined by analyses of ultrafiltrates), was higher than the theoretical amount required to convert the lead to the triphosphate and corresponded more nearly to the diphosphate. Brooks explained his results by assuming a delayed equilibrium in which the dilead phosphate was first formed. At the end of 70 hours, the ratio of lead to phosphorus still corresponded to the dilead phosphate. Bischoff