Acta pharmacol. et toxicol. 1976, 39,256-261.
From The Wihuri Research Institute, SF-00140 Helsinki 14, Finland
Elimination of Thallium in Rats as Influenced by Prussian Blue and Sodium Chloride BY V. Mannincn, Marjatta Malkonen and I. A. Skulskii*
(Received December 3, 1975; Accepted January 27, 1976)
Abstract: The effect of Prussian Blue in protecting rats against lethal doses of thallium was investigated. Treatment with Pntssian Blue increased the survival of rats from 0 % to 50 %. The elimination rate of thallium was increased in all the tissues studied, including the brain. Faecal thallium excretion was increased about three-fold. Treatment with hypertonic sodium chloride improved the shortterm survival but the total mortality was unchanged. Key-words: Thallium poisoning - Prussian Blue - sodium chloride - rat.
In several countries thallium is still widely used as a rodenticide. Thallium poisoning in man has been a therapeutic problem ever since thallium has been used. Many antidotes have been tried and eventually rejected. The latest and most promising approach to the treatment of thallium poisoning has been the use of Prussian Blue, potassium ferric hexacyanoferrate (11), (HEYDLAUP 1969; KAMERBEEK et a[. 1971b; STEVENS et al. 1974). Prussian Blue was first found to accelerate the elimination of radioactive caesium from the body (MADSHUS et al. 1966), the mechanism of which involves the exchange of potassium ions in the lattice of the Prussian Blue molecule for caesium ions. The same mechanism also seems to hold for protection against thallium poisoning, thallium being exchanged for potassium and excreted in the stools. In our experiments we studied the effect of Prussian Blue on the elimination of radioactive thallium in several organs of the rat. The effect of Prussian Blue on the faecal excretion of thallium was also investigated. Thallous ions can influence sodium and potassium transport in a complex el al. 1973 & 1975). Since thallous ions can compete with way (SKULSKII
* Present address: Institute of Evolutionary Physiology and Biochemistry, Academy of Science, Leningrad 194223, U.S.S.R.
PRUSSIAN BLUE AND THALLIUM ELIMINATION
257
sodium ions for the membrane sodium sites, and since high sodium concenef at. 1975), trations are protective in such cases against thallium (SKULSKII the effect of hypertonic sodium chloride on the survival of rats to lethal doses of thallium was also investigated.
Materials and Methods Rats of the Spraque-Dawley strain, weighing about 200 g, were used throughout the study. They were fed with a commercial rat chow (Orion, Helsinki). Food and water was given ad libitum. Prussian Blue was purchased from British Drug Houses (this firm has, however, ceased to produce Prussian Blue and for a small number of experiments Prussian Blue was obtained from Chroma-Gesellschaft, Stuttgart-Untertiirkheim, GFR). 204Tlwas obtained from the Radiochemical Centre, Amersham. Its specific activity was so high that additions of *O4TI practically consisted only of the tracer thallium. Administration of 30 mg/kg of thallium orally (given as thallous sulphate) was found to be lethal in 100% of the rats within 5 days. For the actual experiments this amount of bulk thallium was administered with 10 pci Po4Tl.Prussian Blue was administered orally for 8 days in a daily dose, if not otherwise stated, of 200 mg/kg, devided in two equal parts. Prussian Blue was first administered 12 hrs after administration of thallium. For determination of ao4Tlactivities, rats were sacrificed at I, 2, 3 and 4 days. Tissues were rapidly removed, dried with blotting paper and weighed. For the determination of *O4TI, administered intravenously, stools were removed directly from the large intestine. 204Tlactivity was measured with a y-spectrometer (Wallac, Decem). A standard technique for one compartment analysis was applied for the calculation of 204Tlhalf-lives (MANNINEN1970).
Results Table 1 shows the concentrations of *04T1in various organs at 1 to 4 days after administration of the same amounts of tracer and bulk thallium both to control and Prussian Blue-treated rats. Lower concentrations of '04Tl were detected in all tissues after treatment with Prussian Blue as early as in the first sample, after 1 day. Concentrations of "'Tl varied considerably between various tissues. The highest concentration was noted in the kidneys (table I), while in the liver, heart, muscle (quadriceps), spleen and lung concentrations were intermediate. Red cells accumulated thallium only to a slight extent, the cell/plasma concentration ratios being only slightly above unity. When compared with most other tissues the concentration of thallium in the brain was rather low but its elimination rate was slow (table 2). Prussian Blue drastically accelerated the disappearance of thallium from all organs. When 2"4Tl was administered intravenously and the normal amount of
258
V. MANNINEN, MARJATTA MALKONEN AND I. A. SKULSKlI
Table 1. Thallium concentration as counts per minute per g tissue (wet weight) in various organs of the rat during treatment with Prussian Blue (PB) and in the controls (C).
1st day
Kidney Liver Brain Heart Muscle Spleen Lung Red cells Plasma
2nd day
3rd day
4th day
C
PB
C
PB
C
PB
C
PB
1960 470 300 730 860 670 600 47 35
1950 270 200 420 590 420 360 41 29
1210 560 270 640 760 620 480 55 35
1200 270 210 420 560 455 330 35 30
1020 430 230 530 640 490 400 50 33
550 160 120 210 3 15 200 250 27 20
850 230 160 320 430 320 275 32 27
290 95 80 130 190 140 120 20 19
bulk thallium was given orally, Prussian Blue significantly increased the excretion of 204Tlin the stools (table 3). Treatment with Prussian Blue greatly increased the survival of rats on doses of 30 mg/kg thallium (table 4), which were lethal to lOOVo of the control rats within 5 days. Twelve out of 25 rats treated with 200 mg/kg/day Prussian Blue survived (48Vo). In a group of 10 rats administration of 100 mg/kg/day Prussian Blue was equally efficient while only two rats treated with 30 mg/kg/day Prussian Blue survived. Rats treated with hypertonic sodium chloride tolerated thallium somewhat longer than the control rats. The long-term survival, however, was not changed.
Table 2. Half-life of 204Tl (d-l) in various organs of the control and Prussian Blue-treated rats. Control
Prussian Blue
3.2 1.6 4.1 3.6 3.6 2.1 2.8
1.2 1.4 1.4 1.2 1.3 1.1 1.3
~~
Kidney Liver Brain Heart Muscle Spleen Lungs
259
PRUSSIAN BLUE AND THALLIUM ELIMINATION
Table 3. Faecal excretion of 204T1 as counts per minute per g faeces (dry weight). 1st day
2nd day
3rd day
4200 15300
4300 16200
5800 16300
Control Prussian Blue
In these experiments tracer thallium was administered intravenously and 30 mg/kg thallium was given orally.
Discussion The present results clearly demonstrate the protective effect of Prussian Blue against lethal doses of thallium in rats. Treatment with Prussian Blue increased the survival of rats poisoned by 30 mg/kg thallium from 070 to 50 70. The half-life of thallium was shortened drastically by Prussian Blue in all tissues, including the brain. Some antidotes, like sodium diethyldithiocarbamate and probably other chelating agents too, used in the treatment of thallium poisoning have been reported to lead to a dangerous redistribution of thallium in the brain (KAMERBEEK et a/. 1971a). Faecal excretion of thallium was increased about three-fold by Prussian Blue. Thallium is secreted into the gut via bile and the intestinal mucosa. In the gut potassium ions in the lattice of the Prussian Blue molecule are exchanged for thallium. Binding of thallium into the Prussian Blue molecule et al. 1971b) is stable in the conditions prevailing in the gut (KAMERBEEK and thus elimination of thallium from the body is increased. Retarded bowel function is a common finding in thallium poisoning and thus the elimination of thallium could be still further increased by the use of laxatives.
Table 4. Survival of the various groups of rats. Initial
lstd
2ndd 3rdd
4thd
5thd
Control
17
17/17
17/17 13/17
2/17
0/17
Prussian Blue 200 mglkgld 100 mg/kg/d 30 mg/kg/d
25 10 10
25/25 loll0 lO/lO
25/25 23/25 10/10 l o l l 0 l o l l 0 8/10
8
818
Sodium chloride 14 mmol/kg/d
818
818
18/25 13/25 8/10 6/10 5/10 3/10 518
2/8
6 t h d 30thd
12/25 5/10 2/10 0/8
12/25 5/10 2/10
260
V. MANNINEN, MARJATTA MALK6NEN AND I. A. SKULSKTI
Prussian Blue is non-toxic, at least during such short-term treatment periods as are needed for the treatment of thallium poisoning, and its use is also et al. 1971b; recommended in cases of human thallotoxicosis (KAMERBEEK STEVENS et al. 1974). In the body thallous ions behave much like potassium ions (GEHRLNG & HAMMOND 1967) and administration of potassium chloride is recommended for increasing thallium excretion by the kidneys (LUND1956). Thallium ions et al. 1973). They compete with easily penetrate cell membranes (SKULSKII sodium ions at the same sites, at which an increase in the sodium concenet al. 1975). Hence an attration is protective against thallium (SKULSKII tempt was made t o see whether administration of hypertonic sodium chloride could have any effect against thallium. Sodium chloride was given at a dose (14 mmol/kg) known to cause a profound redistribution of sodium, potassium and hydrogen ions in man, sodium ions being transported into the & SALMINEN 1964). Although rats treated with sodium cells (LUOMANMAKI chloride lived somewhat longer than the control rats, their survival in thallium poisoning was not improved. It appears that sodium ions, in fact, can give some support against thallium at the cellular level. Excretion of potas&. sium in urine is increased by hypertonic sodium chloride (LUOMANMXKI SALMINEN 1964). To what extent excretion of thallium is increased is not known. However, the increment does not seem to be of practical magnitude and importance because the long-term survival is not improved by the administration of sodium chloride.
REFERENCES Gehring, P. J. & P. B. Hammond: The interrelationship between thallium and potassium in animals. J. Pharmacol. Exp. Therap. 1967, 155, 187-201. Heydlauf, H.: Ferric-cyanoferrate (11): An effective antidote in thallium poisoning. Eur. J . Pharmacol. 1969, 6 , 340-344. Kamerbeek, H. H., A. G. Rauws, M.ten Ham & A. N. P. van Heijst: Dangerous redistribution of thallium by treatment with sodium diethyldithiocarbamate. Acta med. scand. 1971a, 189, 149-154. Kamerbeek, H. H., A. G. Rauws, M.ten Ham & A. N. P. van Heijst: Prussian Blue in therapy of thallitoxicosis. Acta rned. scand. 1971b, 189, 321-324. Luomanmaki, K. & S. Salminen: Ion shifts produced by hypertonic sodium chloride infusions in man. Ann. Med. exp. Fenn. 1964, 42, 12-75, Lund, A,: The effect of various substances on the excretion and the toxicity of thallium in the rat. Acta pharmacol. et toxicol. 1956, 12, 260-268. Madshus, K., A. Stromme, F. Bohne & V. Nigrovik: Diminution of radiocesium body burden in dogs and human beings by Prussian Blue. I n t . J . Radiat. Biol. 1966, 10, 5 19-520. Manninen, V.: Movements of sodium and potassium ions and their tracers in propranolol-treated red cells and diaphragm muscle. Acta physiol. scand. 1970, 72, Suppl. 355, 1-76.
PRUSSIAN BLUE AND THALLIUM ELIMINATION
26 1
Skulskii, I. A., V. Manninen & J. Jarnefelt: Interaction of thallous ions with the cation transport mechanism in erythrocytes. Biochem. Biophys. Acta 1973, 298, 702-709. Skulskii, I. A., V. Manninen & J. Jarnefelt: Thallium inhibition of ouabain-sensitive sodium transport and of the (Na+ + K+)-ATPase in human erythrocytes. Biochem. Biophys. Acta 1975, 394, 569-576. Stevens, W., C. van Peteghem, A. Heyndrickx & F. Barbier: Eleven cases of thallium intoxication treated with Prussian Blue. Int. J. Clin. Pharmacol. 1974, 10, 1-22.
From The Wihuri Research Institute, SF-00140 Helsinki 14, Finland
Elimination of Thallium in Rats as Influenced by Prussian Blue and Sodium Chloride BY V. Mannincn, Marjatta Malkonen and I. A. Skulskii*
(Received December 3, 1975; Accepted January 27, 1976)
Abstract: The effect of Prussian Blue in protecting rats against lethal doses of thallium was investigated. Treatment with Pntssian Blue increased the survival of rats from 0 % to 50 %. The elimination rate of thallium was increased in all the tissues studied, including the brain. Faecal thallium excretion was increased about three-fold. Treatment with hypertonic sodium chloride improved the shortterm survival but the total mortality was unchanged. Key-words: Thallium poisoning - Prussian Blue - sodium chloride - rat.
In several countries thallium is still widely used as a rodenticide. Thallium poisoning in man has been a therapeutic problem ever since thallium has been used. Many antidotes have been tried and eventually rejected. The latest and most promising approach to the treatment of thallium poisoning has been the use of Prussian Blue, potassium ferric hexacyanoferrate (11), (HEYDLAUP 1969; KAMERBEEK et a[. 1971b; STEVENS et al. 1974). Prussian Blue was first found to accelerate the elimination of radioactive caesium from the body (MADSHUS et al. 1966), the mechanism of which involves the exchange of potassium ions in the lattice of the Prussian Blue molecule for caesium ions. The same mechanism also seems to hold for protection against thallium poisoning, thallium being exchanged for potassium and excreted in the stools. In our experiments we studied the effect of Prussian Blue on the elimination of radioactive thallium in several organs of the rat. The effect of Prussian Blue on the faecal excretion of thallium was also investigated. Thallous ions can influence sodium and potassium transport in a complex el al. 1973 & 1975). Since thallous ions can compete with way (SKULSKII
* Present address: Institute of Evolutionary Physiology and Biochemistry, Academy of Science, Leningrad 194223, U.S.S.R.
PRUSSIAN BLUE AND THALLIUM ELIMINATION
257
sodium ions for the membrane sodium sites, and since high sodium concenef at. 1975), trations are protective in such cases against thallium (SKULSKII the effect of hypertonic sodium chloride on the survival of rats to lethal doses of thallium was also investigated.
Materials and Methods Rats of the Spraque-Dawley strain, weighing about 200 g, were used throughout the study. They were fed with a commercial rat chow (Orion, Helsinki). Food and water was given ad libitum. Prussian Blue was purchased from British Drug Houses (this firm has, however, ceased to produce Prussian Blue and for a small number of experiments Prussian Blue was obtained from Chroma-Gesellschaft, Stuttgart-Untertiirkheim, GFR). 204Tlwas obtained from the Radiochemical Centre, Amersham. Its specific activity was so high that additions of *O4TI practically consisted only of the tracer thallium. Administration of 30 mg/kg of thallium orally (given as thallous sulphate) was found to be lethal in 100% of the rats within 5 days. For the actual experiments this amount of bulk thallium was administered with 10 pci Po4Tl.Prussian Blue was administered orally for 8 days in a daily dose, if not otherwise stated, of 200 mg/kg, devided in two equal parts. Prussian Blue was first administered 12 hrs after administration of thallium. For determination of ao4Tlactivities, rats were sacrificed at I, 2, 3 and 4 days. Tissues were rapidly removed, dried with blotting paper and weighed. For the determination of *O4TI, administered intravenously, stools were removed directly from the large intestine. 204Tlactivity was measured with a y-spectrometer (Wallac, Decem). A standard technique for one compartment analysis was applied for the calculation of 204Tlhalf-lives (MANNINEN1970).
Results Table 1 shows the concentrations of *04T1in various organs at 1 to 4 days after administration of the same amounts of tracer and bulk thallium both to control and Prussian Blue-treated rats. Lower concentrations of '04Tl were detected in all tissues after treatment with Prussian Blue as early as in the first sample, after 1 day. Concentrations of "'Tl varied considerably between various tissues. The highest concentration was noted in the kidneys (table I), while in the liver, heart, muscle (quadriceps), spleen and lung concentrations were intermediate. Red cells accumulated thallium only to a slight extent, the cell/plasma concentration ratios being only slightly above unity. When compared with most other tissues the concentration of thallium in the brain was rather low but its elimination rate was slow (table 2). Prussian Blue drastically accelerated the disappearance of thallium from all organs. When 2"4Tl was administered intravenously and the normal amount of
258
V. MANNINEN, MARJATTA MALKONEN AND I. A. SKULSKlI
Table 1. Thallium concentration as counts per minute per g tissue (wet weight) in various organs of the rat during treatment with Prussian Blue (PB) and in the controls (C).
1st day
Kidney Liver Brain Heart Muscle Spleen Lung Red cells Plasma
2nd day
3rd day
4th day
C
PB
C
PB
C
PB
C
PB
1960 470 300 730 860 670 600 47 35
1950 270 200 420 590 420 360 41 29
1210 560 270 640 760 620 480 55 35
1200 270 210 420 560 455 330 35 30
1020 430 230 530 640 490 400 50 33
550 160 120 210 3 15 200 250 27 20
850 230 160 320 430 320 275 32 27
290 95 80 130 190 140 120 20 19
bulk thallium was given orally, Prussian Blue significantly increased the excretion of 204Tlin the stools (table 3). Treatment with Prussian Blue greatly increased the survival of rats on doses of 30 mg/kg thallium (table 4), which were lethal to lOOVo of the control rats within 5 days. Twelve out of 25 rats treated with 200 mg/kg/day Prussian Blue survived (48Vo). In a group of 10 rats administration of 100 mg/kg/day Prussian Blue was equally efficient while only two rats treated with 30 mg/kg/day Prussian Blue survived. Rats treated with hypertonic sodium chloride tolerated thallium somewhat longer than the control rats. The long-term survival, however, was not changed.
Table 2. Half-life of 204Tl (d-l) in various organs of the control and Prussian Blue-treated rats. Control
Prussian Blue
3.2 1.6 4.1 3.6 3.6 2.1 2.8
1.2 1.4 1.4 1.2 1.3 1.1 1.3
~~
Kidney Liver Brain Heart Muscle Spleen Lungs
259
PRUSSIAN BLUE AND THALLIUM ELIMINATION
Table 3. Faecal excretion of 204T1 as counts per minute per g faeces (dry weight). 1st day
2nd day
3rd day
4200 15300
4300 16200
5800 16300
Control Prussian Blue
In these experiments tracer thallium was administered intravenously and 30 mg/kg thallium was given orally.
Discussion The present results clearly demonstrate the protective effect of Prussian Blue against lethal doses of thallium in rats. Treatment with Prussian Blue increased the survival of rats poisoned by 30 mg/kg thallium from 070 to 50 70. The half-life of thallium was shortened drastically by Prussian Blue in all tissues, including the brain. Some antidotes, like sodium diethyldithiocarbamate and probably other chelating agents too, used in the treatment of thallium poisoning have been reported to lead to a dangerous redistribution of thallium in the brain (KAMERBEEK et a/. 1971a). Faecal excretion of thallium was increased about three-fold by Prussian Blue. Thallium is secreted into the gut via bile and the intestinal mucosa. In the gut potassium ions in the lattice of the Prussian Blue molecule are exchanged for thallium. Binding of thallium into the Prussian Blue molecule et al. 1971b) is stable in the conditions prevailing in the gut (KAMERBEEK and thus elimination of thallium from the body is increased. Retarded bowel function is a common finding in thallium poisoning and thus the elimination of thallium could be still further increased by the use of laxatives.
Table 4. Survival of the various groups of rats. Initial
lstd
2ndd 3rdd
4thd
5thd
Control
17
17/17
17/17 13/17
2/17
0/17
Prussian Blue 200 mglkgld 100 mg/kg/d 30 mg/kg/d
25 10 10
25/25 loll0 lO/lO
25/25 23/25 10/10 l o l l 0 l o l l 0 8/10
8
818
Sodium chloride 14 mmol/kg/d
818
818
18/25 13/25 8/10 6/10 5/10 3/10 518
2/8
6 t h d 30thd
12/25 5/10 2/10 0/8
12/25 5/10 2/10
260
V. MANNINEN, MARJATTA MALK6NEN AND I. A. SKULSKTI
Prussian Blue is non-toxic, at least during such short-term treatment periods as are needed for the treatment of thallium poisoning, and its use is also et al. 1971b; recommended in cases of human thallotoxicosis (KAMERBEEK STEVENS et al. 1974). In the body thallous ions behave much like potassium ions (GEHRLNG & HAMMOND 1967) and administration of potassium chloride is recommended for increasing thallium excretion by the kidneys (LUND1956). Thallium ions et al. 1973). They compete with easily penetrate cell membranes (SKULSKII sodium ions at the same sites, at which an increase in the sodium concenet al. 1975). Hence an attration is protective against thallium (SKULSKII tempt was made t o see whether administration of hypertonic sodium chloride could have any effect against thallium. Sodium chloride was given at a dose (14 mmol/kg) known to cause a profound redistribution of sodium, potassium and hydrogen ions in man, sodium ions being transported into the & SALMINEN 1964). Although rats treated with sodium cells (LUOMANMAKI chloride lived somewhat longer than the control rats, their survival in thallium poisoning was not improved. It appears that sodium ions, in fact, can give some support against thallium at the cellular level. Excretion of potas&. sium in urine is increased by hypertonic sodium chloride (LUOMANMXKI SALMINEN 1964). To what extent excretion of thallium is increased is not known. However, the increment does not seem to be of practical magnitude and importance because the long-term survival is not improved by the administration of sodium chloride.
REFERENCES Gehring, P. J. & P. B. Hammond: The interrelationship between thallium and potassium in animals. J. Pharmacol. Exp. Therap. 1967, 155, 187-201. Heydlauf, H.: Ferric-cyanoferrate (11): An effective antidote in thallium poisoning. Eur. J . Pharmacol. 1969, 6 , 340-344. Kamerbeek, H. H., A. G. Rauws, M.ten Ham & A. N. P. van Heijst: Dangerous redistribution of thallium by treatment with sodium diethyldithiocarbamate. Acta med. scand. 1971a, 189, 149-154. Kamerbeek, H. H., A. G. Rauws, M.ten Ham & A. N. P. van Heijst: Prussian Blue in therapy of thallitoxicosis. Acta rned. scand. 1971b, 189, 321-324. Luomanmaki, K. & S. Salminen: Ion shifts produced by hypertonic sodium chloride infusions in man. Ann. Med. exp. Fenn. 1964, 42, 12-75, Lund, A,: The effect of various substances on the excretion and the toxicity of thallium in the rat. Acta pharmacol. et toxicol. 1956, 12, 260-268. Madshus, K., A. Stromme, F. Bohne & V. Nigrovik: Diminution of radiocesium body burden in dogs and human beings by Prussian Blue. I n t . J . Radiat. Biol. 1966, 10, 5 19-520. Manninen, V.: Movements of sodium and potassium ions and their tracers in propranolol-treated red cells and diaphragm muscle. Acta physiol. scand. 1970, 72, Suppl. 355, 1-76.
PRUSSIAN BLUE AND THALLIUM ELIMINATION
26 1
Skulskii, I. A., V. Manninen & J. Jarnefelt: Interaction of thallous ions with the cation transport mechanism in erythrocytes. Biochem. Biophys. Acta 1973, 298, 702-709. Skulskii, I. A., V. Manninen & J. Jarnefelt: Thallium inhibition of ouabain-sensitive sodium transport and of the (Na+ + K+)-ATPase in human erythrocytes. Biochem. Biophys. Acta 1975, 394, 569-576. Stevens, W., C. van Peteghem, A. Heyndrickx & F. Barbier: Eleven cases of thallium intoxication treated with Prussian Blue. Int. J. Clin. Pharmacol. 1974, 10, 1-22.
