Biological effects of the enhanced excretion of zinc after calcium diethylenetriaminepentaacetate chelation therapy

Zinc deficiency induced by the chelating agent DTPA and its regulatory interpretation for developmental toxicity classification

Aminocarboxylic acid (ethylenediamine-based) chelating agents such as DTPA are widely used in a variety of products and processes. Recently, DTPA was classified in the European Union as a developmental toxicant CLP Category 1B. However, according to the CLP regulation (CLP, 2008) classification as a developmental toxicant requires a chemical to possess an intrinsic, specific property to do so. This paper provides overwhelming evidence that shows the developmental toxicity only seen at a sustained high dose of 1000 mg DTPA/kg bw/day in rats during pregnancy is mediated by zinc depletion which leads to non-specific secondary effects associated with zinc deficiency. Therefore, based on the CLP regulation itself, viz. the lack of a specific, intrinsic property, supported by significant differences in zinc kinetics and physiology between pregnant rats and pregnant women, DTPA should not be classified as a developmental toxicant. Moreover, classification for developmental toxicity resulting from zinc deficiency, and only observed at high doses, would not increase protection of human health; instead, it will only lead to onerous and disproportionate restrictions being placed on the use of this substance.

Grouping approaches based on structure alone are insufficient to conclude about toxicological properties-the example of monoamine-based chelates

Aminocarboxylic acid (monoamine-based) chelating agents such as GLDA, MGDA, NTA, and EDG are widely used in a variety of products and processes. In the European Union, based on the Green Deal and the Chemicals Strategy for Sustainability (CSS), there is an increasing tendency to speed up chemical hazard evaluation and to regulate chemicals by grouping substances based on molecular structure similarity. Recently, it was proposed to group polycarboxylic acid monoamines, hydroxy derivatives and their salts with monovalent cations, and to consider all group members as potential carcinogens based on the official CLP classification of one group member, viz. NTA, which is classified as suspected carcinogen Cat. 2. In this review, we show that a grouping approach for harmonized classification and labeling based on molecular structure alone, disregarding existing animal test data as well as current scientific and regulatory knowledge, would result in incorrect classification. Using such a simplistic, although considered pragmatic approach, classification of all group members upfront would not improve protection of human health. Instead, it could not only lead to unnecessary additional vertebrate animal testing but also to onerous and disproportionate restrictions being placed on the use of these valuable substances; some of these even being considered as green chemicals.

Effects of the chelating agent DTPA on naturally accumulating metals in the body

Diethylenetriaminepentaacetate (DTPA) is the most widely used chelating agent for Pu and Am. Volunteers were assigned to receive intravenous injections or aerosol inhalations of 1 g of DTPA on days 1-4; volunteers received once daily injections of CaDTPA or ZnDTPA, CaDTPA inhalation as an aerosol, or CaDTPA injection on day 1 and ZnDTPA on days 2-4. CaDTPA injection or inhalation increased the excretion rates of Zn in urine with concomitantly reduced levels of serum Zn. Injection of CaDTPA reduced activities of serum alkaline phosphatase (AP) in parallel with the kinetics of Zn, whereas CaDTPA and ZnDTPA injection reduced activities of lactate dehydrogenase (LDH), and reduced activities of creatinine kinase (CK) were observed upon CaDTPA injection and its inhalation. Intravenous administration of CaDTPA and ZnDTPA enhanced excretion rates of Mn in urine, whereas transient reduction of Mn levels in serum was detected only via CaDTPA injection. Both CaDTPA and ZnDTPA transiently reduced levels of Mg in serum without affecting the excretion rates. On the other hand, both DTPAs increased excretion rates of toxic metals such as Pb and Cd, and CaDTPA also increased the rates of Hg. These results suggest that DTPA, and especially CaDTPA, removes essential metals and that the activities of these metalloenzymes are good indicators for the imbalance of essential metals during the DTPA administration. Our results also show that CaDTPA injection is more potent for removing these metals than ZnDTPA and inhalation of CaDTPA, and DTPA may be useful for the treatment of acute heavy metal poisoning with Pb, Cd, or Hg.

Effect of ethanol on the retention of americium-241 in the baboon liver

The oral administration of ethyl alcohol enhanced the excretion of 241Am from the liver of a baboon by 2.5 times that of a control animal. After ethanol administration, increases in the total content of 241Am excreted in feces were accompanied by corresponding increases in fecal volumes, although administration of nonalcoholic cathartics would not be expected to produce a similar effect. The effectiveness of ethanol as a decorporating agent may result from its ability to mobilize intracellularly bound 241Am from the liver, thereby making the nuclide more available for metabolic secretory mechanisms occurring via liver-bile-fecal route.

On the influence of Ca-DTPA on delta-aminolevulinic acid dehydratase in rats

In rats red cell delta-aminolevulinic acid dehydratase is inhibited by Ca-DTPA only after treatment with toxic doses or with fractionated therapeutic doses. Zn-DTPA does not influence the activity of the enzyme even after administration of high doses.