Ken-ichi Sano

Inhibitory effect of methylmercury on the activity of glutathione peroxidase

Inhibitory effect of methylmercuric chloride (MMC) on the activity of glutathione peroxidase was studied using 100,000g supernatant of the liver homogenate from 10 male SPF Wistar rats in vitro. Marked inhibition of glutathione peroxidase activity was observed between concentrations of 5 × 10−6 and 5 × 10−5 m MMC, but the activity was hardly inhibited at concentrations less than 5 × 10−6 m MMC; inhibition was almost complete at concentrations greater than 5 × 10−5 m MMC.

Modulating effects of biogenic amines on calcium and ethanol-induced sleeping time

The present study was carried out in order to clarify the mechanism of calcium prolongation of ethanol-induced sleep. p-Chlorophenylalanine (PCPA, 300 mg/kg), alpha-methyltyrosine (alpha MPT, 100 mg/kg) and diethyldithiocarbamate (DDC, 250 mg/kg) were administered intraperitoneally (IP) to mice to reduce the levels of serotonin (5-HT), dopamine (DA) and norepinephrine (NE) respectively in the brain. Sleeping time was then measured following the administration of ethanol (4.5 g/kg, IP) both with and without CaCl2 (20 mumol/kg, intravenous (IV)). When saline (IP) plus CaCl2 (IV) was administered, the duration of ethanol-induced sleep was prolonged by 100% as compared with saline (IP) plus saline (IV). Duration of ethanol-induced sleep was not changed by PCPA, alpha MPT and DDC. On the other hand, the prolongation of ethanol-induced sleep by CaCl2 was antagonized by PCPA, alpha MPT and DDC. Also, only the DA level in the cerebrum was increased by 25% by administration of CaCl2. We suggest that the increase in ethanol-induced sleeping time due to CaCl2 results from the increase in biogenic amines in the brain.

Effects of environmental temperatures on the toxicity of methylmercury in rats.

The study was designed to examine the influence of environmental temperatures on subacute (5 mg/kg/3 days) methylmercury toxicity in rats by observations of mortality, manifestation of the hindleg-crossing phenomenon, and measurement of total and methylmercury in tissue samples.

The effect of L-cysteine on the portion-selective uptake of cadmium in the renal proximal tubule

Cadmium (Cd), co-administered with an excess of L-cysteine, accumulates rapidly in the kidneys of the rat. After subcutaneous (s. c.) injection of 3 μmol CdCl2/kg body wt the concentrations of Cd in the blood and kidneys increase with the dose of cysteine over the range 0.06–5.0 mmol/kg body wt. At cysteine doses of less than 1.5 mmol/kg body wt the ratio of the concentrations of Cd in the outer medulla and cortex of the kidney remains the same as that after the injection of Cd alone. This ratio, however, is more than doubled at dose levels of 5–10 mmol cysteine/kg body wt. Hepatic uptake of Cd is unaffected by doses of cysteine below 1.5 mmol/kg body wt but decreases markedly at higher doses. In animals that are dosed simultaneously with 5 mmol cysteine/kg body wt, renal uptake of 109Cd is known to occur in the straight segments of the proximal tubules. At a dose level of less than 1.5 mmol cysteine/kg body wt the present autoradiographical studies show that 109Cd is taken up predominantly by the proximal convoluted tubules of the kidney cortex. At the critical dose level (1.5 mmol/kg body wt), cysteine decreases the retention of Cd at the s. c. injection site, but probably has little effect on the distribution of Cd between protein and other carrier molecules in the blood. This distribution, however, is altered at higher cysteine dose levels. It is suggested that, under the latter conditions, stable Cd-cysteine complexes are formed in the blood and are filtered readily through the glomeruli. These complexes are taken up in the kidney at the sites of cysteine reabsorption which, by studies with L-[35S]-cysteine, are identified as the straight segments of the proximal tubules.

Autoradiographical studies on the localization of metallothionein in proximal tubular cells of the rat kidney.

The renal distribution of 125I-labelled metallothionein (125I-MT), administered as a tracer dose to female Wistar rats, has been investigated by light and electron microscopical autoradiography. 125I-MT was absorbed rapidly and 80% of the administered dose was observed in the kidney within 60 min after dosing. At 30 min, a high density of silver grains due to 125I, was observed by light microscopy in the convoluted proximal tubules. Electron microscopical autoradiography showed that silver grains were located in large apical vacuoles and cytoplasmic bodies (heterolysosomes) of the endocytotic system in the apical or middle regions of the cells lining convoluted proximal tubules. The results suggest that endocytotic systems are associated with 125I-MT absorption by epithelial cells lining the renal convoluted proximal tubules. The apparent inconsistency on the distribution pattern of silver grains due to 109Cd-labelled MT and 125I-labelled MT in these is also discussed.

Discovery of methyl mercury compound in dry batteries

Abstract The mercury compounds used in dry cell batteries are inorganic mercurials. This report clarifies the possible formation of methyl mercury compounds in the contents of batteries obtained on the market. Using gas chromatography-mass spectrometry it was confirmed that the substance extracted from the ingredients is methyl mercury chloride.