Yasuhiro Yamane

Effect of Zinc Pretreatment on Mercuric Chloride-Induced Lipid Peroxidation in the Rat Kidney

The effect of zinc on mercuric chloride-induced lipid peroxidation in the rat kidney was investigated. The rats received zinc acetate (2.0 mmol/kg, po) for 2 days before being given mercuric chloride (15 mumol/kg, sc) and were killed 6, 12, and 24 hr after the last injection. Lipid peroxidation occurred in the rat kidney 12 hr after mercury administration, and this mercury-induced lipid peroxidation was significantly reduced by zinc pretreatment. A decrease in vitamin C and E contents in the kidney was observed 12 hr after the administration of mercury, and this decrease was prevented by zinc pretreatment. In the kidney of rats pretreated with zinc, the activities of the protective enzymes, glutathione peroxidase and glucose-6-phosphate dehydrogenase, were increased after mercury injection. Non-protein sulfhydryl content (mostly glutathione) also rose markedly. The results indicate that zinc not only induces metallothionein, but also increases protective enzyme activities and glutathione content, which would tend to inhibit lipid peroxidation and suppress mercury toxicity.

Mechanism of protection by zinc against mercuric chloride toxicity in rats: Effects of zinc and mercury on glutathionine metabolism

To investigate the mechanism by which zinc suppresses mercury toxicity, the effects of zinc and mercury on glutathione (GSH) metabolism in the rat kidney were studied. When the time course of GSH level in the rat kidney was examined at 2, 6, and 12 h after treatment of rats with both metals, an increase of GSH was found and was apparently related to the activation of some GSH-associated enzymes. In the kidney of rats treated with both metals, the response of the protective function involving GSH and GSH-associated enzymes depended on the magnitude of mercury toxicity but appeared to be independent of the zinc dosage. The administration of diethyl maleate (DEM), which depletes GSH, increased lipid peroxidation and mercury toxicity concomitantly with a decrease of GSH level in the kidney of rats treated with zinc and mercury. In conclusion, the data suggest that an increased GSH level in the kidney resulting from the activation of GSH-associated enzymes plays a role in the protective effect of zinc against mercury toxicity.

Mutagenicity of airborne particles

The mutagenicity of airborne particles was studied in the Ames Salmonella system. The mutagenic activity of benzene extracts from airborne particles was more active in strain TA98 in the presence and absence of S9 mix than in strain TA100. The presence of mutagens, other than benzo[a]pyrene (B[a]P), which did not require S9 mix, was indicated. However, the monthly variation of direct-acting mutagenic activity showed a pattern similar to that of B[a]P at atmospheric concentration. The monthly variations of atmospheric NO, NO2, NO-2 and NO-3 concentrations were also similar to that of the direct-acting mutagenic activity. Atmospheric concentrations of heavy metals such as Pb, Zn, Cd, V and Cu were also found to be related to direct-acting mutagenic activity. These results suggest that emissions from automobiles, home heaters and power plants etc. may be a primary source of atmospheric, direct-acting mutagens. It is suggested that secondary direct-acting mutagens might be partly formed by the nitration of polycyclic aromatic hydrocarbons (PAH) with NO2 in the atmosphere because concentrations of B[a]P, NO2 and NO-3 increased simultaneously when the highest direct-acting mutagenic activity was observed.

Simultaneous determination of residual synthetic antibacterials in fish by high-performance liquid chromatography

A simple and rapid high-performance liquid chromatographic (HPLC) method for the simultaneous determination of sulphamonomethoxine (SMMX), sulphadimethoxine (SDMX), sulphisozole (SIZ), nalidixic acid (NA), oxolinic acid (OXA), piromidic acid (PMA), furazolidone (FZ) and sodium nifurstyrenate (NFSA) in cultured fish was developed. The drugs were extracted with 0.2% metaphosphoric acid-methanol (6:4), followed by a Bond Elut C18 clean-up procedure. The HPLC separation was carried out on an Inertsil ODS column (150 x 4.6 mm I.D.) using 5 mM aqueous oxalic acid-acetonitrile (55:45) as the mobile phase with detection at 265 nm (0.04 a.u.f.s.). The calibration graphs were rectilinear from 1 to 20 ng for OXA, from 2 to 50 ng for SMMX, SDMX, SIZ, NA, PMA and FZ and from 5 to 100 ng for NFSA. The recoveries of each drug added to fish were 65.0-89.5%. The detection limits were 0.02 micrograms/g for OXA, 0.05 micrograms/g for SMMX, SDMX, SIZ, NA, PMA and FZ and 0.1 micrograms/g for NFSA.

Preventive effect of zinc against cadmium-induced bone resorption

The effects of cadmium and zinc on bone resorption were investigated using fetal mouse calvaria organ culture. Cadmium treatment (0.5 microM) stimulated bone resorption in fetal mouse calvaria via prostaglandin E2 production. Concomitant treatment of zinc with cadmium prevented bone resorption by cadmium in a dose-dependent manner of zinc. The zinc treatment also prevented the stimulation of prostaglandin E2 production by cadmium. ID50 of zinc for bone resorption showed high similarity to that for prostaglandin E2 production (1.2 microM and 1.6 microM, respectively). To simplify the system, we used osteoclast-enriched and osteoblast-enriched cell populations obtained from mice calvariae by collagenase digestion method. Prostaglandin E2 was produced in osteoblast-enriched cell culture more than in osteoclast-enriched cell culture. Cadmium stimulated prostaglandin E2 production in osteoblast-enriched cell culture, but not in osteoclast-enriched cell culture. Zinc also prevented the stimulatory effect of cadmium on prostaglandin E2 production in osteoblast-enriched cell culture. Zinc partially, but significantly, inhibited cadmium-accumulation in both calvaria and osteoblast-enriched cell culture. These results strongly suggest that zinc prevents cadmium-induced prostaglandin E2 production and bone resorption through the interaction between the two metals on osteoblasts involved in the inhibition of cadmium-accumulation.

Cadmium stimulates prostaglandin E2 synthesis in osteoblast-like cells, MC3T3-E1

The effect of Cd on prostaglandin E2 production in osteoblasts was studied using cloned osteoblast-like cells, MC3T3-E1, which were established from new-born mouse calvaria. Treatment of the cells with Cd caused a dose- (0-10 microM) and time- (0-24 h) dependent increase in the release of prostaglandin E2 from the cells into the culture medium. A lag time of 4 h was required for the onset of the phenomenon. The release of [14C]arachidonic acid from prelabeled cell membrane was little influenced by the Cd treatment, while conversion of [14C]arachidonic acid to prostaglandin E2 by the homogenate of the cells treated with Cd was enhanced as compared to that by untreated cells. The stimulatory effect of Cd on prostaglandin E2 production was abolished in the presence of cycloheximide (100 ng/ml). By Western blot analysis with polyclonal rabbit anti-cyclooxygenase antibody, it was revealed that Cd treatment augmented the amount of immunoreactive cyclooxygenase in the cells. These results strongly suggest that Cd stimulates prostaglandin E2 production through the induction of cyclooxygenase in MC3T3-E1 cells. This effect of Cd may be involved in the mechanisms of Cd-induced bone injury.

Protective effect of sodium molybdate against the acute toxicity of cadmium chloride

Pretreatment of rats with Na2MoO4 (1.24 mmol/kg, once a day for 3 days, i.p.) partially protected them against the acute toxicity of CdCl2 (0.075 mmol/kg, once, s.c., 24 h after pretreatment with Na2MoO4). The survival number of rats per total number of rats in the CdCl2-dosed group was 10/10, 8/10, 6/10, 2/10 and 0/10 on 0, 1, 2, 6 and 18 days after treatment with CdCl2 whereas in the group where CdCl2 is given after pretreatment with Na2MoO4 it is 10/10 and 6/10 on 0 and 18 days. The body weight of CdCl2-dosed rats consistently decreased until their death while that of Na2MoO4-CdCl2-dosed rats similarly decreased up to 4 days after exposure to CdCl2 but then increased almost normally. In order to elucidate the mechanism of protective action of Na2MoO4 against the acute toxicity of CdCl2, cellular components such as DNA, inorganic cations and metallothionein were measured in the liver after exposure to CdCl2. The treatment with CdCl2 alone reduced K content and increased Ca content but pretreatment with Na2MoO4 prevented such alterations in the levels of those cations caused by CdCl2. Metallothionein content in the liver was significantly elevated in the CdCl2-treated groups as compared to saline controls although the protein content was higher in the Na2MoO4-CdCl2-dosed group than in the CdCl2-dosed group. There was no difference in the protein content of the liver between saline controls and the Na2MoO4-dosed group. This suggests that Na2MoO4 alleviated the acute toxicity of CdCl2 in the rat and the protective mechanism by the metal is in part related to the enhancement of liver Cd-metallothionein induction.

An immunological study of a Pb-thionein like protein in rat liver

Administration of a sublethal dose of lead acetate to rats induced the simultaneous synthesis of a Pb-thionein like protein (Pb-BP) and Zn-thionein in the liver. To determine of the Pb-BP is a species of metallothionein, immunological properties of this protein were investigated. The results indicate that the Pb-BP is cross-reactive with the antibody against rat Zn-thionein II, strongly suggesting that the Pb-BP is a metallothionein.

Protective effect of sodium molybdate on the acute toxicity of mercuric chloride. V. Enhancement of renal regeneration after exposure to HgCl2

Pretreatment with Na2MoO4 protected rats from HgCl2-induced decreases in the renal concentration of amino acids, RNA, DNA, ATP and dry matter. It also reduced the mercury-induced increases in renal water, Ca and serum creatinine. Ma2MoO4 considerably elevated the RNA/DNA ratio in the renal cortex after treatment with HgCl2. In addition, subcellular distribution of mercury was markedly altered by pretreatment with Na2MoO4, specifically Na2MoO4 pretreatment decreased the mercury content in the particulate fractions such as the nuclei and mitochondria while increasing the mercury content of the cytosol. Sephadex G-75 gel filtration showed that the increase in mercury content in the cytosol of Na2MoO4-pretreated rats is due to an increase in the metal content of a metallothionein-like fraction. These results suggest that Na2MoO4-pretreatment protects against HgCl2 renal toxicity by stimulating mercury-mediated metallothionein induction in the renal cortex and renal regenerative processes.

Correlations among atmospheric elements, airborne particulate matter, benzene extracts, benzo(a)pyrene, NO, NO2 and so2 concentrations in Japan

Abstract Concentration levels of elements, airborne particulate matter, benzene extracts, benzo(a)pyrene B(a)P, NO, NO2 and SO2 in five residential areas were seasonally determined from May 1979 to January 1980. These air pollutants exhibited higher concentration in autumn and winter than in spring and summer. These were correlations among Pb, Cu, Ni, V and Se, among Si, Fe, Al and Ti and among NO, NO2, B(a)P, benzene extracts and airborne particulate matter. NO, NO2, B(a)P, benzene extracts and airborne particulate matter were correlated with Pb, Cu, Ni, V and Se, but not appreciably with Si, Fe, Al and Ti. On the basis of correlations between various air pollutants, the emitting source of the air pollutants and the health hazard by combined air pollution were discussed.