Effect of ethylenediaminetetraacetic acid on deposition and excretion of certain rare earth elements.

The study was carried out by determining the effect of calcium ethylenediaminetetraacetate on the excretion and distribution in rats of a number of rare earths and yttrium, and correlating the magnitude of these effects with the stability constants of the chelates formed with some of the rare earths. These rare earths were selected because they form a long series of closely related elements with similar chemical and physical properties and because the stability constants of the chelates formed with ethylenediaminetetraacetic acid (EDTA) have been determined (1). Yttrium was studied because of its close relationship to the rare earths. The following isotopes’ were used: Ce144, Pmlr7, Tb160, Ygl, and Trn”O. The isotopes were administered, either essentially carrier-free or with trace amounts of carrier, intravenously in 0.5 per cent sodium citrate solution at, pH 5 to male Sprague-Dawley rats weighing 300 gm. Ten animals were injected with each isytope. Half of the animals were given 200 mg. of Ca EDTA intraperitoneally per kilo once daily for 4 days. Urine and feces were collected and assayed daily. At the end of 4 days, all of the animals were killed, and liver, spleen, and long bones (humeri, radii, ulnae, femorae, and tibiae, including all epiphyses) were removed. The remainder of the carcass was assayed as a unit. In preparation for counting, the tissues were dry ashed and the ash was dissolved in 6 N HNOS. Cerium, yttrium, terbium, and thulium were counted in a scintillation