Morio Kiyozumi

Comparative effects of three chelating agents on distribution and excretion of cadmium in rats

Sodium N-benzyl-D-glucamine dithiocarbamate (NBG-DTC), which was newly synthesized, 2,3-dimercaptopropanol (BAL), and N-methyl-D-glucamine dithiocarbamate (NMG-DTC) were compared for their relative efficacies in the distribution and excretion of cadmium in rats exposed to cadmium. Rats were injected ip with 109CdCl2 (1 mg Cd and 10 microCi 109Cd/kg) and 3 days later, they were treated with the chelating agents (400 mumol/kg) every other day for 2 weeks. These chelating agents were effective in removing cadmium from the body without increasing the amount of cadmium in the kidney. After treatment with these chelating agents, cadmium was excreted mainly in the feces through the bile and the fecal excretion of cadmium by NBG-DTC was significantly larger than that by BAL or NMG-DTC. The hepatic cadmium content after treatment with NBG-DTC was much more decreased than that with BAL or NMG-DTC. The renal cadmium content was decreased only after treatment with NBG-DTC. These chelating agents did not result in the redistribution of cadmium to brain, testes, and heart. The growth of rats was little retarded by treatment with NBG-DTC and NMG-DTC, but was retarded by treatment with BAL. The treatment with NBG-DTC decreased the tissue amounts of Zn, Fe, and Mn to a small extent as compared with the treatment with cadmium alone. The results of this study reveal that the injection of NBG-DTC to rats pretreated with cadmium can more effectively remove cadmium from the body without the mobilization of cadmium to the kidney, the critical organ in cadmium toxicity, and without redistribution of cadmium to other tissues such as brain, testes, and heart, than injection of BAL and NMG-DTC.

Effects of dithiocarbamates on testicular toxicity in rats caused by acute exposure to cadmium

N-Benzyl-D-glucamine dithiocarbamate (BGD), N-p-isopropylbenzyl-D-glucamine dithiocarbamate (PBGD), and diethyl-dithiocarbamate (DED) were compared for their protective effects against the testicular toxicity in rats induced by acute exposure to cadmium. Rats were injected subcutaneously with 109CdCl2 (3 mg Cd and 74 kBq of 109Cd/kg) and 30 min later, they were injected intraperitoneally with the chelating agents (0.4 or 3 mmol/kg). Cadmium injection increased lipid peroxidation and concentrations of hemoglobin and Ca in the testes, decreased the testicular weight, and caused sterility. The treatment with BGD (0.4 mmol/kg) did not satisfactorily protect against the testicular toxicity of cadmium. The administration of PBGD or DED at a dose of 3 mmol/kg significantly prevented the increase in the lipid peroxidation and hemoglobin concentration in the testes, the decrease in the testicular weight, and the sterility caused by cadmium. PBGD and DED significantly decreased the cadmium concentration in the testes, but DED increased the cadmium concentration in the kidney and brain. Only DED significantly prevented the increase in the testicular Ca concentration after cadmium. These results indicate that PBGD and DED protect against the sterility caused by cadmium in rats and that the effect of DED to increase the brain level of cadmium is more dangerous than the lack of effect of PBGD to prevent the increase in the testicular Ca level. The protective effects of PBGD and DED against the cadmium-induced testicular toxicity presumably result from a decrease in the cadmium concentration in the testes.

Effect of N-benzyl-d-glucamine dithiocarbamate on distribution and excretion of cadmium in rats

The effect of sodium N-benzyl-D-glucamine dithiocarbamate (NBG-DTC) on the distribution and excretion of cadmium in rats exposed to cadmium and the chemical form and intestinal reabsorption of cadmium compound excreted in the bile were studied. Rats were injected intraperitoneally with 109CdCl2 (1 mg Cd and 10 microCi 109Cd/kg) and 24 h later, they were injected with NBG-DTC (400 or 1200 mumol/kg). The biliary excretion of cadmium was remarkably increased by intraperitoneally injection of NBG-DTC, while there was only a small increase in urinary excretion of cadmium. Such an enhancement effect of NBG-DTC on the biliary excretion of cadmium was much larger at the high dose (1200 mumol/kg) of NBG-DTC. The treatment with NBG-DTC significantly decreased the cadmium content in the liver at the dose of 1200 mumol/kg and did not result in the undesirable redistribution of cadmium to the tissues, such as brain, testes, heart and lung. In addition, it was found that the cadmium compound excreted in the bile was mainly characterized as cadmium-NBG-DTC and which was not reabsorbed from the intestinal tracts.

Effect of N-benzyl-D-glucamine dithiocarbamate on the renal toxicity produced by subacute exposure to cadmium in rats.

The effect of N-benzyl-D-glucamine dithiocarbamate (BGD) on the renal toxicity produced by subacute exposure to cadmium in rats was studied. Rats were injected sc with CdCl2 (1.5 mg Cd/kg) daily for 26 days and thereafter they received 13 injections of BGD (400 mumol/kg) every other day. Urinary protein concentration and AST activity significantly increased after 20 days of cadmium treatment. The pattern of the increase in the urinary excretion of cadmium after cadmium treatment was consistent with that in the urinary excretion of protein and AST. Urinary excretion of amino acid increased gradually after the cessation of cadmium treatment. BGD treatment significantly decreased the urinary excretion of protein, aspartate aminotransferase (AST), and amino acid. Plasma AST activity was elevated 8 days after the beginning of cadmium treatment, indicating that the hepatic damage occurred prior to the renal damage. In addition, the microscopic examination of renal tissue from cadmium-treated rats revealed the necrosis of the proximal tubular cells. The cadmium concentrations in liver and kidney were significantly decreased by BGD treatment. The results of this study indicate that BGD treatment is effective in decreasing the cadmium concentrations in liver and kidney, resulting in the therapeutic effect on the cadmium-induced renal damage.

Protective Effects of Dithiocarbamates against Renal Toxicity of cis-Diamminedichloroplatinum in Rats

Sodium diethyldithiocarbamate (DDTC), sodium N-benzyl-D-glucamine dithiocarbamate (BGD), sodium N-p-hydroxymethylbenzyl-D-glucamine dithiocarbamate (HBGD), and sodium N-p-carboxybenzyl-D-glucamine dithiocarbamate (CBGD) were evaluated for efficacy as inhibitors of cis-diamminedichloroplatinum (DDP)-induced nephrotoxicity in a rat model. Treatments with 2.0 mmol/kg of BGD, HBGD, and CBGD immediately after DDP (20 mumol/kg) injection effectively prevented the nephrotoxic effects of DDP, but administration of DDTC immediately after DDP injection afforded a small protection. Concurrent treatment with 0.5 or 1.0 mmol/kg of HBGD, or 1.0 mmol/kg of CBGD could prevent DDP-induced renal damage. A significant decrease in weight loss was also observed in these dithiocarbamate-rescued rats. The platinum concentrations in liver and kidney were significantly decreased by BGD, HBGD, and CBGD treatments, respectively. The antitumor efficacy of DDP in the Walker 256 carcinoma-bearing rats was not affected by administration of HBGD (1.0 mmol/kg) or CBGD (1.0 mmol/kg). The results of this study indicated that the injection of HBGD or CBGD to rats treated with DDP can protect against DDP-induced nephrotoxicity more effectively than DDTC or BGD.

Further study of effects of chelating agents on excretion of inorganic mercury in rats

The effects of three chelating agents, N-benzyl-D-glucamine dithiocarbamate (BGD), 2,3-dimercaptopropanol (BAL) and D-penicillamine (D-PEN), on the excretion of mercury in rats exposed to mercuric chloride (HgCl2), the chemical forms of mercury compounds excreted in the bile and urine and the intestinal reabsorption of mercury compounds in the bile were studied. Rats were injected intraperitoneally with 203HgCl2 (300 micrograms Hg and 74 kBq of 203Hg/kg) and 24 h later, they were injected intraperitoneally with a chelating agent (a quarter of an LD50). The injection of the chelating agents significantly enhanced the biliary and urinary excretions of mercury. The enhancing effect of BGD on the excretions of mercury was almost the same as that of BAL and much larger than that of D-PEN. The major chemical form of mercury in the bile and urine of rats injected with BGD after HgCl2 treatment was Hg-BGD compounds. The chemical form of mercury in the bile and urine of rats injected with BAL after HgCl2 treatment was mainly Hg-GSH compound. The mercury after HgCl2 and D-PEN treatment was excreted mainly via the urine in the form of Hg-D-PEN compound. The intestinal reabsorption of mercury from the bile of rats injected with BGD or D-PEN was only 0.18% or 0.38% of the dose, respectively. The intestinal reabsorption of mercury from the bile of rats injected with BAL was 27.38% of the dose. It was suggested that the Hg-GSH compound excreted in the bile after HgCl2 and BAL treatment is partly degraded to Hg-cysteine (Cys) by the intestinal membranous enzymes and that the ligand of Hg-Cys is replaced by BAL in the bile, resulting in the effective reabsorption of Hg-BAL compound from the intestine.

Protection against cis-diamminedichloroplatinum-induced nephrotoxicity in rats by N-benzyl-D-glucamine dithiocarbamate

Sodium N-benzyl-D-glucamine dithiocarbamate (BGD) was evaluated for its efficacy as an inhibitor of cis-diamminedichloroplatinum (DDP)-induced nephrotoxicity in a rat model. Treatment with 2.0 mmol/kg of BGD immediately after DDP injection effectively prevented nephrotoxic effects of DDP, but administration of BGD -1 or 1 h after DDP afforded a small protection. Concurrent treatment with 0.5 mmol/kg of BGD could not prevent renal damage. The platinum concentrations in liver and kidney were significantly decreased by BGD treatment. The antitumor efficacy of DDP in the Walker 256 carcinoma-bearing rats was not affected by administration of BGD (2.0 mmol/kg).

A possible mechanism of resistance to cadmium toxicity in male Long-Evans rats

The susceptibility to cadmium (Cd)-induced toxicity in male Long-Evans (LE) rats was compared with that in male Fischer 344 (Fischer) and Wistar-Imamichi (WI) rats, which are sensitive and resistant, respectively, to Cd toxicity. All rats of the LE and WI strains survived for 7 days after the treatment with a toxic dose of Cd (6.5mg/kg b.w.). However, all rats of the Fischer strain died by the following day. The strong resistance to Cd toxicity in the LE strain was confirmed to be independent of metallothionein synthesis induced by Cd. The hepatic and renal Cd contents after its administration were significantly lower in the LE strain than in the Fischer strain. Furthermore, the hepatic and renal zinc (Zn) contents after its administration were significantly lower in the LE strain than in the Fischer strain. These limited data suggest that the strong resistance to Cd toxicity in male LE rats results from, at least in part, the lower accumulation of the metal in the liver and kidney, in a similar mechanism as the lower Zn accumulation.

Comparative effects of N,N-disubstituted dithiocarbamates on excretion and distribution of cadmium in mice

Sodium N-benzyl-D-glucamine dithiocarbamate (BGD), sodium N-p-hydroxymethylbenzyl-D-glucamine dithiocarbamate (HBGD), sodium N-p-carboxybenzyl-D-glucamine dithiocarbamate (CBGD) and sodium N-p-methoxybenzyl-D-glucamine dithiocarbamate (MeOBGD) were evaluated for their efficacy in the distribution and excretion of cadmium in mice exposed to cadmium. Mice were injected i.p. with 109CdCl2 (1 mg Cd/kg and 74 kBq of 109Cd/animal) and 30 min or 24 h later, they were injected with chelating agents (400 mumol/kg). At 30 min after treatment with cadmium, these chelating agents all significantly enhanced the biliary excretion of cadmium, and HBGD and CBGD significantly increased the urinary excretion of the metal. At 24 h after cadmium injection, BGD, HBGD, and MeOBGD significantly increased the biliary excretion of cadmium and HBGD was the most effective on the biliary excretion of the metal. These chelating agents were effective in mobilizing cadmium from the liver at 30 min after cadmium treatment. At 24 h after cadmium treatment, HBGD and MeOBGD effectively depressed cadmium content in the liver and only HBGD among these chelating agents significantly reduced the cadmium content in the kidney. In another experiment, mice were injected i.p. with 109CdCl2 and three days later, they were injected with chelating agents every other day for 2 weeks. HBGD was the most effective on the fecal and urinary excretions of cadmium. The hepatic cadmium content was decreased after HBGD or MeOBGD injection. The injection of HBGD caused a much greater decrease in renal cadmium content than did BGD, CBGD, or MeOBGD. The results of this study indicated that the injection of HBGD to mice pretreated with cadmium can remove cadmium from the body, mainly through fecal excretion, without redistribution of cadmium to other tissues such as the brain, testes, and heart, more effectively than that of BGD, CBGD, or MeOBGD.

Urinary metabolites of 2,6-diisopropylnaphthalene in rats.

Metabolism of 2,6-diisopropylnaphthalene (2,6-DIPN) in rats was found to proceed exclusively through oxidation of the isopropyl chain of the molecule. Five unconjugated metabolites were isolated from the urine and identified: 2,6-naphthalenedi(2-propan)-2-ol, 2-[6-(1-hydroxy-1-methyl)ethylnaphthalen-2-yl]-2-propionic acid, 2,6-naphthalenedi-2-propionic acid, 2-[6-(1-hydroxy-1-methyl)ethylnaphthalen-2-yl]-2-hydroxypropionic acid, and 2-[6-(1-hydroxy-1-methyl)ethylnaphthalen-2-yl]-1,2-propanediol, together with a small amount of the unchanged compound. The identification of these metabolites was made by means of mass, infrared, and nuclear magnetic resonance spectrometry. The presence of glucuronides of five metabolites described above was also suggested by thin-layer and gas-liquid chromatography of the extract that was obtained after hydrolysis by beta-glucuronidase. In addition, the quantitative determination of metabolites indicated that these five were the major urinary metabolites of 2,6-DIPN, and that the total urinary excretion of these metabolites in 24 hr after administration was about 23% of the dose.