Abstract

The effects of calcium sodium ethylenediaminetetra-acetate (CaNa₂EDTA) on the kinetics of distribution and excretion of lead (²¹⁰Pb) have been studied in rats. When the chelant was given intravenously, at 50 mg./rat daily after a single intravenous injection of 100 μg. lead/rat, it greatly increased the urinary excretion of lead but reduced the faecal excretion. The greatest effects occurred in the rats treated with chelant shortly after the lead injection. When the chelant was given seven or more days after the lead the increase in lead excretion was negligible. CaNa₂EDTA mobilized lead from every tissue, but the kinetic analysis of the disappearance of ²¹⁰Pb showed the presence of two elimination phases. Lead ions weakly bound to the cells were rapidly removed by EDTA, whereas the lead fixed to endocellular constituents was only slowly removed. The chelant did not mobilize lead from bone.

Probably CaNa₂EDTA entered the extravascular space but not the cells. Hence it only accelerated the passage of lead from the cells by lowering the concentration of lead outside them.

²¹⁰Pb was also given orally in doses of 500 μg. lead/rat. About 18% of the dose was absorbed through the intestine to be distributed in all tissues. Rats treated orally with CaNa₂EDTA showed an increase in urinary lead excretion and a reduction in lead fixed in the body.