- Email: [email protected]
Ratio of organs to blood of mercury during its uptake by normal and acatalasemic mice
ENVIRONMENTAL RESEARCH 42, 421-424 (1987)
Ratio of Organs to Blood of Mercury during Its Uptake by Normal and Acatalasemic Mice M. OGATA AND H. AIKOH Department of Public Health, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama City, Japan 700 Received July 10, 1984 The brain/blood, liver/blood, and heart/blood ratios of acatalasemic mice after intraperitoneal injection of metallic mercury or after exposure to metallic mercury vapor were significantly higher than those of normal mice. These ratios of normal or acatalasemic mice after injection with metallic mercury or exposure to metallic mercury vapor were significantly higher than those of normal and acatalasemic mice injected with mercuric ion. The amount of metallic mercury exhaled from acatalasemic mice injected with metallic mercury was greater than that from normal mice, indicating that the level o f metallic mercury in blood of the former was higher than that of the latter. Actually, metallic mercury in the blood of acatalasemic mice injected with metallic mercury is higher than that in the blood o f normal mice, suggesting that metallic mercury is easily transfered from blood to brain, liver, kidney, and heart. © 1987AcademicPress, Inc.
INTRODUCTION Metallic mercury is rapidly oxidized by catalase to mercuric ion when animals are exposed to metallic mercury vapor. Kudsk (1969) reported that ethyl alcohol depressed the pulmonary absorption of metallic mercury vapor. Magos et al. (1973) found that alcohol affected the in vivo oxidation rate of metallic mercury, i.e., the amount of metallic mercury vapor exhaled from rats injected with metallic mercury was higher in rats pretreated with ethyl alcohol than that in untreated control rats. The authors (Ogata and Ikeda, 1978) also reported that erythrocyte and lung and liver homogenates prepared from acatalasemic mice exhibited decreased activities in vitro in the uptake of mercury as compared with normal mice. Acatalasemic mice (Ogata et al., 1981) had decreased levels of mercury in the lungs and blood when they were exposed to metallic mercury vapor. In our previous studies (Ogata et al., 1985), mercury uptake in various organs in normal and acatalasemic mice exposed to metallic mercury vapor was found to be different. The present report deals with organ/blood ratios during its uptake by normal and acatalasemic mice.
MATERIALSAND METHODS Normal and acatalasemic mice, weighing 20-25 g, were exposed to metallic mercury vapor (2°3Hg°) or injected intraperitoneally with metallic mercury (2°3Hg°) or mercuric chloride (2°3HGC12) solution. One hour after treatment, the mice were anesthetized with diethyl ether and blood samples were taken from orbital veins. Organs were removed and washed 421 0013-9351/87 $3.00 Copyright@ 1987by AcademicPress, Inc. All rightsof reproductionin any form reserved.
422
OGATA AND AIKOH
TABLE 1 ORGAN/BLOOD RATIOS OF NORMAL AND ACATALASEMIC MICE INJECTED INTRAPERITONEALLY WITH METALLIC MERCURY AND MERCURIC CHLORIDE OR EXPOSED TO METALLIC MERCURY VAPORa
Organ/blood
Species
Brain/blood
2°3Hg° (inj.)
N A N A N A N A
Liver/blood Kidney/blood Heart/blood
0.067 0.500 3.467 7.250 7.449 7.815 0.448 0.755
-+ 0.004 _+ 0.003 -+ 0.052 _+ 0.052 _+ 1.934 -+ 0.018 _+ 0.018 _+ 0.097
2°3HGC12 (inj.) 0.025 0.026 0.704 1.130 15.020 24.360 0.349 0.533
_+ _+ -+ _+ _+ -+ -+ _+
2°3Hg° (exp.)
0.001 0.001 0.003 0.005 1.064 4.264 0.140 0.139
1.951 3.214 1.605 5.893 11.321 20.262 6.434 14.018
+ 0.375 _+ 0.432 _+ 0.049 _+ 0.073 _+ 1.975 -+ 3.409 +_ 1.085 -4- 0.977
a N, normal mice; A, acatalasemic mice. Metallic mercury (2°3Hg°) was prepared from 2°3HGC12 and ascorbic acid.
in saline. The total mercury content was determined by a Multi-Mode Scaler
(Aloka Co., TDC-601). RESULTS The brain/blood ratios of mercury were highest in exposure experiments with metallic mercury vapor and next highest with metallic mercury injection in both normal and acatalasemic mice. Higher brain/blood ratios of mercury in acatalasemic mice than in normal mice were found with metallic mercury injection and metallic mercury vapor inhalation. The brain/blood, liver/blood, and heart/blood ratios of acatalasemic mice receiving metallic mercury injection or exposed to metallic mercury vapor were significantly higher than those of normal mice, respectively (Tables 1 and 2). The amount of metallic mercury exhaled from acatalasemic mice injected with metallic mercury was greater than that exhaled from normal mice, indicating that the blood level of metallic mercury in the former was higher than that of the latter (Fig. 1). The amount of metallic mercury exhaled from acatalasemic mice injected with mercuric ion was higher than that of similarly treated normal mice as described previously (Ogata et al., 1984, 1987). The level of metallic mercury in the blood of acatalasemic mice injected with metallic mercury was higher than that of TABLE 2 SIGNIFICANCE LEVELS FOR THE DIFFERENCES BETWEEN PAIRS OF ORGAN/BLOOD RATIOS OF NORMAL AND ACATALASEMIC MICE a
Organ/blood Brain/blood Liver/blood Kidney/blood Heart/blood
2°3Hg° (inj.)
203HGC12(inj.)
203Hg°(exp.)
N-A
N-A
N-A
P< P< P> P<
0.05 0.05 0.05 0.05
P> P< P> P>
0.05 0.05 0.05 0.05
P< P< P< P<
0.05 0.05 0.05 0.05
2°3Hg° (inj.)203HGC12(inj.) N-N P< P< P< P>
0.05 0.05 0.05 0.05
2°3HgClz (inj.)2°3Hg° (exp.)
A-A P< P< P< P>
0.05 0.05 0.05 0.05
N-N P< P< P> P<
0.05 0.05 0.05 0.05
A-A P< P< P> P<
0.05 0.05 0.05 0.05
a Level of significance for the differences between normal and acatalasemic mice was calculated using the t-test or Welch's test.
423
ORGAN/BLOOD RATIOS OF MERCURY Exhalation
Blood
¢
Metallic mercury
t ~
Organs
Metallic mercury
Brain
Mercuric
Heart
Normal
ion Lungs Normal Liver Metallic
Metallic
mercury
mercury Kidneys
Acatalasemia Mercuric
Intestines
ion
Acatalasemia FIG. 1. Transformation of mercury in blood of normal and acatalasemic mice.
similarly treated normal mice (Ogata and Aikoh, 1984). The partition coefficient to octanol/water of metallic mercury is about two times higher than that of mercuric ion, indicating that metallic mercury has more lipotrophic property than mercuric ion.
DISCUSSION The foregoing data indicate that lipotrophic metallic mercury in the blood passed through the blood-brain barrier, the brain having a higher concentration of metallic mercury in the blood. Similar results were obtained in the liver and heart of acatalasemic mice exposed to metallic mercury vapor. Data indicate that the ratio of organ to blood in acatalasemic mice is higher than that of normal mice. Metallic mercury in the blood of acatalasemic mice or the amount of meTABLE 3 CATALASE ACTIVITY IN ORGANS OF NORMAL AND ACATALASEMIC MICE
Catalase activity (PU/g) a Organ Brain Heart Lung Liver Kidney Blood
Normal/acatalasemia 2.12 6.16 8.38 6.66 20.54 37.70
_+ 0.49 + 1.49 _+ 0.28 _+ 1.36 _+ 1.98 -4- 4.82 b
a Catalase activity in organs was calculated using the perborate method. b PU/ml Hb.
424
OGATA AND AIKOH
tallic mercury exhaled from acatalasemic mice is higher than that of normal mice, respectively. This may be explained by assuming that the catalase activity in the brain, liver, kidney, and heart of acatalasemic mice has sufficient activity to fix metallic mercury as mercuric ion (Table 3). Metallic mercury in the blood and its lipotrophic properties may determine the distribution of metallic mercury to the brain, liver, kidney, and heart, in that lipotrophic metallic mercury passed through the brain-blood barrier resulting in a higher concentration of metallic mercury in the brain. The kidney/blood ratios were lower in mice injected with metallic mercury or in mice exposed to metallic mercury vapor than in those injected with mercuric ion, indicating that mercuric ion was accumulated in the kidneys. ACKNOWLEDGMENT The authors express their thanks to Dr. Kazuhisa Taketa for his help in preparing this manuscript.
REFERENCES Kudsk, F. N. (1969). Factors influencing the in vitro uptake of mercury vapor in blood. Acta Pharmacol. Toxicol. 27, 161-172. Magos, L., Clarkson, T. W., and Greenwood, M. R. (1973). The depression of pulmonary retention of mercury vapor by ethanol: Identification of the site of action. ToxicoL Appl. Pharmacol. 26, 160-183. Ogata, M., and Ikeda, M. (1978). Mercury uptake by acatalasemia mice and their erythrocytes, lung and liver homogenates. Int. Arch. Occup. Environ. Health 41, 87-93. Ogata, M., Kanematsu, S., Morita, K., and Yuasa, T. (1981). Organ distribution of mercury vapor inhaled by acatalasemia and hypocatalasemia mice. Ind. Health 19, 241-246. Ogata, M., and Aikoh, H. (1984). Mercury concentration in the blood and organs of normal and acatalasemic mice after intraperitoneal injection of metallic mercury (2°3Hg°). Physiol. Chem. Phys. & Med. N M R . 16, 71-73. Ogata, M., Kenmotsu, K., Hirota, N., Meguro, T., and Aikoh, H. (1985). The mercury uptake in vivo by normal and acatalasemic mice exposed to metallic mercury vapor (Z°3Hg°) and injected with metallic mercury or mercuric chloride (2°3HGC12).Arch. Environ. Health 40, 151-154. Ogata, M., Kenmotsu, K., Hirota, N., Meguro, T., and Aikoh, H. (1987). Reduction of mercuric ion and exhalation of mercury in acatalasemic and normal mice. Arch. Environ. Health, in press.
Ratio of Organs to Blood of Mercury during Its Uptake by Normal and Acatalasemic Mice M. OGATA AND H. AIKOH Department of Public Health, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama City, Japan 700 Received July 10, 1984 The brain/blood, liver/blood, and heart/blood ratios of acatalasemic mice after intraperitoneal injection of metallic mercury or after exposure to metallic mercury vapor were significantly higher than those of normal mice. These ratios of normal or acatalasemic mice after injection with metallic mercury or exposure to metallic mercury vapor were significantly higher than those of normal and acatalasemic mice injected with mercuric ion. The amount of metallic mercury exhaled from acatalasemic mice injected with metallic mercury was greater than that from normal mice, indicating that the level o f metallic mercury in blood of the former was higher than that of the latter. Actually, metallic mercury in the blood of acatalasemic mice injected with metallic mercury is higher than that in the blood o f normal mice, suggesting that metallic mercury is easily transfered from blood to brain, liver, kidney, and heart. © 1987AcademicPress, Inc.
INTRODUCTION Metallic mercury is rapidly oxidized by catalase to mercuric ion when animals are exposed to metallic mercury vapor. Kudsk (1969) reported that ethyl alcohol depressed the pulmonary absorption of metallic mercury vapor. Magos et al. (1973) found that alcohol affected the in vivo oxidation rate of metallic mercury, i.e., the amount of metallic mercury vapor exhaled from rats injected with metallic mercury was higher in rats pretreated with ethyl alcohol than that in untreated control rats. The authors (Ogata and Ikeda, 1978) also reported that erythrocyte and lung and liver homogenates prepared from acatalasemic mice exhibited decreased activities in vitro in the uptake of mercury as compared with normal mice. Acatalasemic mice (Ogata et al., 1981) had decreased levels of mercury in the lungs and blood when they were exposed to metallic mercury vapor. In our previous studies (Ogata et al., 1985), mercury uptake in various organs in normal and acatalasemic mice exposed to metallic mercury vapor was found to be different. The present report deals with organ/blood ratios during its uptake by normal and acatalasemic mice.
MATERIALSAND METHODS Normal and acatalasemic mice, weighing 20-25 g, were exposed to metallic mercury vapor (2°3Hg°) or injected intraperitoneally with metallic mercury (2°3Hg°) or mercuric chloride (2°3HGC12) solution. One hour after treatment, the mice were anesthetized with diethyl ether and blood samples were taken from orbital veins. Organs were removed and washed 421 0013-9351/87 $3.00 Copyright@ 1987by AcademicPress, Inc. All rightsof reproductionin any form reserved.
422
OGATA AND AIKOH
TABLE 1 ORGAN/BLOOD RATIOS OF NORMAL AND ACATALASEMIC MICE INJECTED INTRAPERITONEALLY WITH METALLIC MERCURY AND MERCURIC CHLORIDE OR EXPOSED TO METALLIC MERCURY VAPORa
Organ/blood
Species
Brain/blood
2°3Hg° (inj.)
N A N A N A N A
Liver/blood Kidney/blood Heart/blood
0.067 0.500 3.467 7.250 7.449 7.815 0.448 0.755
-+ 0.004 _+ 0.003 -+ 0.052 _+ 0.052 _+ 1.934 -+ 0.018 _+ 0.018 _+ 0.097
2°3HGC12 (inj.) 0.025 0.026 0.704 1.130 15.020 24.360 0.349 0.533
_+ _+ -+ _+ _+ -+ -+ _+
2°3Hg° (exp.)
0.001 0.001 0.003 0.005 1.064 4.264 0.140 0.139
1.951 3.214 1.605 5.893 11.321 20.262 6.434 14.018
+ 0.375 _+ 0.432 _+ 0.049 _+ 0.073 _+ 1.975 -+ 3.409 +_ 1.085 -4- 0.977
a N, normal mice; A, acatalasemic mice. Metallic mercury (2°3Hg°) was prepared from 2°3HGC12 and ascorbic acid.
in saline. The total mercury content was determined by a Multi-Mode Scaler
(Aloka Co., TDC-601). RESULTS The brain/blood ratios of mercury were highest in exposure experiments with metallic mercury vapor and next highest with metallic mercury injection in both normal and acatalasemic mice. Higher brain/blood ratios of mercury in acatalasemic mice than in normal mice were found with metallic mercury injection and metallic mercury vapor inhalation. The brain/blood, liver/blood, and heart/blood ratios of acatalasemic mice receiving metallic mercury injection or exposed to metallic mercury vapor were significantly higher than those of normal mice, respectively (Tables 1 and 2). The amount of metallic mercury exhaled from acatalasemic mice injected with metallic mercury was greater than that exhaled from normal mice, indicating that the blood level of metallic mercury in the former was higher than that of the latter (Fig. 1). The amount of metallic mercury exhaled from acatalasemic mice injected with mercuric ion was higher than that of similarly treated normal mice as described previously (Ogata et al., 1984, 1987). The level of metallic mercury in the blood of acatalasemic mice injected with metallic mercury was higher than that of TABLE 2 SIGNIFICANCE LEVELS FOR THE DIFFERENCES BETWEEN PAIRS OF ORGAN/BLOOD RATIOS OF NORMAL AND ACATALASEMIC MICE a
Organ/blood Brain/blood Liver/blood Kidney/blood Heart/blood
2°3Hg° (inj.)
203HGC12(inj.)
203Hg°(exp.)
N-A
N-A
N-A
P< P< P> P<
0.05 0.05 0.05 0.05
P> P< P> P>
0.05 0.05 0.05 0.05
P< P< P< P<
0.05 0.05 0.05 0.05
2°3Hg° (inj.)203HGC12(inj.) N-N P< P< P< P>
0.05 0.05 0.05 0.05
2°3HgClz (inj.)2°3Hg° (exp.)
A-A P< P< P< P>
0.05 0.05 0.05 0.05
N-N P< P< P> P<
0.05 0.05 0.05 0.05
A-A P< P< P> P<
0.05 0.05 0.05 0.05
a Level of significance for the differences between normal and acatalasemic mice was calculated using the t-test or Welch's test.
423
ORGAN/BLOOD RATIOS OF MERCURY Exhalation
Blood
¢
Metallic mercury
t ~
Organs
Metallic mercury
Brain
Mercuric
Heart
Normal
ion Lungs Normal Liver Metallic
Metallic
mercury
mercury Kidneys
Acatalasemia Mercuric
Intestines
ion
Acatalasemia FIG. 1. Transformation of mercury in blood of normal and acatalasemic mice.
similarly treated normal mice (Ogata and Aikoh, 1984). The partition coefficient to octanol/water of metallic mercury is about two times higher than that of mercuric ion, indicating that metallic mercury has more lipotrophic property than mercuric ion.
DISCUSSION The foregoing data indicate that lipotrophic metallic mercury in the blood passed through the blood-brain barrier, the brain having a higher concentration of metallic mercury in the blood. Similar results were obtained in the liver and heart of acatalasemic mice exposed to metallic mercury vapor. Data indicate that the ratio of organ to blood in acatalasemic mice is higher than that of normal mice. Metallic mercury in the blood of acatalasemic mice or the amount of meTABLE 3 CATALASE ACTIVITY IN ORGANS OF NORMAL AND ACATALASEMIC MICE
Catalase activity (PU/g) a Organ Brain Heart Lung Liver Kidney Blood
Normal/acatalasemia 2.12 6.16 8.38 6.66 20.54 37.70
_+ 0.49 + 1.49 _+ 0.28 _+ 1.36 _+ 1.98 -4- 4.82 b
a Catalase activity in organs was calculated using the perborate method. b PU/ml Hb.
424
OGATA AND AIKOH
tallic mercury exhaled from acatalasemic mice is higher than that of normal mice, respectively. This may be explained by assuming that the catalase activity in the brain, liver, kidney, and heart of acatalasemic mice has sufficient activity to fix metallic mercury as mercuric ion (Table 3). Metallic mercury in the blood and its lipotrophic properties may determine the distribution of metallic mercury to the brain, liver, kidney, and heart, in that lipotrophic metallic mercury passed through the brain-blood barrier resulting in a higher concentration of metallic mercury in the brain. The kidney/blood ratios were lower in mice injected with metallic mercury or in mice exposed to metallic mercury vapor than in those injected with mercuric ion, indicating that mercuric ion was accumulated in the kidneys. ACKNOWLEDGMENT The authors express their thanks to Dr. Kazuhisa Taketa for his help in preparing this manuscript.
REFERENCES Kudsk, F. N. (1969). Factors influencing the in vitro uptake of mercury vapor in blood. Acta Pharmacol. Toxicol. 27, 161-172. Magos, L., Clarkson, T. W., and Greenwood, M. R. (1973). The depression of pulmonary retention of mercury vapor by ethanol: Identification of the site of action. ToxicoL Appl. Pharmacol. 26, 160-183. Ogata, M., and Ikeda, M. (1978). Mercury uptake by acatalasemia mice and their erythrocytes, lung and liver homogenates. Int. Arch. Occup. Environ. Health 41, 87-93. Ogata, M., Kanematsu, S., Morita, K., and Yuasa, T. (1981). Organ distribution of mercury vapor inhaled by acatalasemia and hypocatalasemia mice. Ind. Health 19, 241-246. Ogata, M., and Aikoh, H. (1984). Mercury concentration in the blood and organs of normal and acatalasemic mice after intraperitoneal injection of metallic mercury (2°3Hg°). Physiol. Chem. Phys. & Med. N M R . 16, 71-73. Ogata, M., Kenmotsu, K., Hirota, N., Meguro, T., and Aikoh, H. (1985). The mercury uptake in vivo by normal and acatalasemic mice exposed to metallic mercury vapor (Z°3Hg°) and injected with metallic mercury or mercuric chloride (2°3HGC12).Arch. Environ. Health 40, 151-154. Ogata, M., Kenmotsu, K., Hirota, N., Meguro, T., and Aikoh, H. (1987). Reduction of mercuric ion and exhalation of mercury in acatalasemic and normal mice. Arch. Environ. Health, in press.