Influence of nitrilotriacetate (NTA) on the toxicity, excretion and distribution of cadmium in female rats

The use of the chelating agent EDTA in the treatment of acute cadmium toxicity, tissue distribution and some blood parameters in the Egyptian toad Bufo regularis

Erythrocyte count, haemoglobin content, haematocrit value, erythrocyte sedimentation rate and cadmium accumulation in some organs and tissues were estimated in toads administered 6.2 mg Cd2+/kg i.m. for 4 days. EDTA therapy caused considerable decrease in all the blood parameters studied. A striking reduction in the cadmium content of all the organs and tissues studied except the kidneys was also observed after simultaneous treatment with EDTA.

Influence of chelating agents on toxicity and distribution of cadmium among proteins of mouse liver and kidney following oral or subcutaneous exposure

Acute toxicity and organ distribution of cadmium was investigated in mice exposed to 1) single subcutaneous doses of 109Cd-labelled cadmium (3.2 mg (0.028 mmol)/kg b.wt.) alone or in combination with nitrilotriacetic acid, NTA (32 mg (0.167 mmol/kg b.wt.) or sodium tripolyphosphate, STPP (32 mg (0.087 mmol/kg b.wt.) and 2) single oral doses of cadmium (60 mg (0.53 mmol/kg b.wt.) alone or together with NTA (600 mg (3.14 mmol)/kg.b.wt.) or STPP (600 mg (1.63 mmol/kg b.wt.) Whole-body retention of radiolabelled cadmium as well as mortality was registered in all groups during 20-21 days. Five hours after exposure, 3-4 mice in each group were killed and cadmium distribution among proteins in liver and kidney studied by gel chromatography on a G-75 Sephadex column. Organ concentration of cadmium was also determined at sacrifice of all other mice after an observation time of 20-21 days. A markedly increased mortality was observed during the first 24 hours after subcutaneous exposure to Cd + NTA (70%) or Cd + STPP (40%) compared to Cd alone (0%). On the contrary, no mortality was seen after oral exposure to Cd + NTA (70%) or CD + STPP (while oral exposure to Cd alone or with NTA resulted in a mortality of about 45% during the same observation time. Five hours after subcutaneous exposure, liver cadmium concentrations were equal in all mice and bound mainly to a low molecular weight protein (probably metallothionein). In kidney, concentrations were about twice as high in mice given Cd + NTA or CD + STPP compared to mice given Cd alone. More cadmium was transferred to the kidneys in the presence of chelating agents. This was further supported by the decreased liver/kidney cadmium concentration ratio between 5 hours and 21 days. The increased mortality in mice given Cd + NTA or Cd + STPP may be due to an initially high accumulation of cadmium in liver, which may exceed the upper limit for metallothionein synthesis, whereby toxic damage of the hepatic cells and leakage of cadmium from the liver would occur. Five hours after oral exposure, cadmium retention in organs of mice given Cd + STPP was 4-6 times lower than in mice given Cd alone, while mice given Cd + NTA had slightly higher organ concentrations. The binding of more cadmium to metallothionein in liver of Cd + STPP-exposed mice 5 hours after exposure, may be due to the lower accumulation of cadmium in these mice compared to those given Cd alone or CD + NTA, where cadmium was bound mainly to high molecular proteins in the liver. After 20 days, mice given CD + STPP has slightly higher body and organ retention of cadmium compared to mice given Cd alone. This may be due to a binding of cadmium to metallothione in these mice which is known to prolong the retention time of cadmium in tissue.

The implications of trace metal-nitrilotriacetetic acid speciation on its environmental impact and toxicology

Substitution of nitrilotriacetic acid (NTA) for polyphosphates in detergents has brought questions concerning its potential toxicity and impact on trace metal distribution in the environment. A calculation based upon metal ligand equilibria, known environmental concentrations of NTA following extensive detergent usage, and the presence of competitive metal-binding ligands and trace elements demonstrates that NTA will be present almost completely as the calcium and magnesium chelates. An analogous estimate of the speciation of NTA in various toxicity studies demonstrates that the onset of chronic toxicity in feeding studies is coincident with the presence of significant concentrations of "free" NTA in the gastrointestinal tract. Massive doses of NTA over long periods of time cause reproducible renal tumors in rats, but dosages of 7500 ppm administered indefinitely are without measurable effect.

Effects of detergent formula chelating agents on the metabolism and toxicity of cadmium in mice

Chelating agents like NTA (nitrilotriacetic acid) STPP (sodiumtripolyphosphate, Na5P3O10) and EDTA (ethylenediaminetetraacetic acid) are used as components of detergents. An increased toxicity of some metal compounds when combined with NTA has led to decreased use of this chelating agent in relation to STPP. In the present studies short-term and long-term effects of these chelating agents on cadmium toxicity in mice were investigated. I: In the short-term study, mice subcutaneously exposed to CdCl2 (3.2 mg Cd/kg b. wt.) in combination with STPP (32 mg/kg b. wt.) demonstrated a markedly higher mortality compared to animals given CdCl2 alone. This increase in mortality was similar to the one encountered when CdCl2 (3.2 mg Cd/kg b. wt.) and NTA (32 mg/kg b. wt.) were combined. Animals exposed subcutaneously to CdCl2 + STPP or CdCl2 + NTA showed histological evidence of liver necrosis 24 hrs after exposure not seen in animals given the same dose of CdCl2 alone and also had markedly lower cadmium concentrations in the livers compared to only Cd-exposed animals. II: In the long-term study, mice were exposed orally to CdSO4 (50p.p.m Cd) alone or in combination with STPP (500 p.p.m.), NTA (500 p.p.m.) or EDTA (50 p.p.m.) by continuous administration via the drinking water for 18 months. A decreased total excretion of urine proteins was seen in all Cd-treated animals irrespectively of the combination with various chelating agents. The conclusion of the present work was the NTA and STPP given by subcutaneous injection to mice markedly increased the toxicity of cadmium but that neither NTA, STPP nor EDTA given orally altered the toxicity of cadmium during a period of long-term exposure of 18 months.