宮崎 良文

1. The action of 1,1,1-trichloroethane (1,1,1-TCE) on cytochrome P-450-dependent mixed-function oxidation by rat liver microsomes was studied by determination of the rates of O2 consumption, H2O2 production, and 1,1,1-TCE metabolism, and from the spectral change in cytochrome P-450. 2. 1,1,1-TCE caused increases in the rate of O2 consumption, and H2O2 production, although metabolism of 1,1,1-TCE was minimal. The stoichiometry of the rate of metabolism of 1,1,1-TCE to the increase in the rate of O2 consumption was about 0·011. The increase in O2 consumption and the production of H2O2 did not occur in microsomes treated with SKandF 525-A. 3. Spectral studies indicated that 1,1,1-TCE bound to cytochrome P-450 and showed a type I spectral change. 4. The addition of NADH with NADPH in the reaction medium enhanced the increase in O2 consumption caused by 1,1,1-TCE, whereas it did not change the rate of H2O2 production. 5. There was no increase in the formation of thiobarbituric acid reactive substances in the reaction medium incubated with 1,1,1-TCE. 6. It was concluded that 1,1,1-TCE had an uncoupling effect on the cytochrome P-450-dependent mixed-function oxidation system. © 1988 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.

The interaction of nitrite with catalase was investigated spectrophotometrically in the perfused rat liver. Real-time spectral changes were obtained using a reflectance scanning spectrophotometer in the liver perfused with a haemoglobin-free medium in a non-recirculating system. Administration of sodium nitrite caused a specific pattern of spectral change indicating the decomposition of catalase compound I to free catalase. The spectral change due to the interaction with nitrite did not occur during potassium cyanide or ethanol infusion, nor in the aminotriazole-pretreated rat liver. The spectral change was observed at concentrations of nitrite in the perfusate over 0.01 mm, and the K0.5 value (the concentration producing half the maximum spectral change) was 0.06 mm. It was concluded that relatively low concentrations of nitrite caused decomposition of catalase compound I in the physiologically functioning liver cell. © 1988.

The metabolism of chloral hydrate (CH) under anoxic conditions was investigated in the non-recirculating, hemoglobin-free liver perfusion system. CH uptake in the anoxic liver decreased to about 80% of that in the oxygen-supplied liver. The reduction of CH to trichloroethanol (TCE) increased and the oxidation of CH to trichloroacetic acid (TCA) decreased. The TCE/TCA ratio increased however, the total trichloro compounds, that is TCE and TCA, were not significantly altered by anoxia. Though approximate 14% of the CH infused into the oxygen-supplied liver was changed to substances other than TCE or TCA, the unknown part was a very small portion in the anoxic liver. The decrease in CH uptake, by the anoxic liver, is thought to be equivalent to the decrease of the unknown metabolites. The TCE/TCA ratio under anoxia was also altered by pyruvate or lactate infusion. © 1988.

©,Chloral hydrate (CH), an intermediate metabolite of trichloroethylene, is reduced to trichloroethanol (TCE) by alcohol dehydrogenase and aldehyde reductase, and is also oxidized to trichloroacetic acid (TCA) by the nicotinamide adenine dinucleotide (NAD)‐dependent enzyme, CH dehydrogenase. Alcohol dehydrogenase requires reduced NAD (NADH), aldehyde reductase requires reduced nicotinamide adenine dinucleotide phosphate (NADPH) and CH dehydrogenase requires NAD to complete the reaction. It is unclear which reaction is predominant at the physiological redox level in intact liver cells. To study this question, we perfused the livers of well‐fed rats with Krebs‐Ringer buffer solution containing 0.1 mM pyruvate/1.0 mM lactate. The levels of TCE and TCA in the effluent were measured by gas chromatography, and the fluorescence of reduced pyridine nucleotides was measured with a surface fluorometer. When a low concentration (below 0.25 mM) of CH was administered, more TCA than TCE was produced. When a high concentration of CH was administered (over 0.5 mM), TCE production was greater. Reduced pyridine nucleotides decreased inversely with the CH concentration. Even at low CH concentrations, pyridine nucleotides were not reduced. When 10 mM lactate was added to the perfusate in order to reduce the pyridine nucleotides in the liver cells, the TCE/TCA ratio increased. On the other hand, the TCE/TCA ratio tended to fall following the addition of 5.0 mM pyruvate. In conclusion, the TCE/TCA ratio was altered according to the concentration of CH, and to the redox level of pyridine nucleotides in the liver.

Changes in the hepatic cytochrome P-450-dependent drug-metabolizing system were studied in perfused livers obtained from cold-acclimated male Wistar rats after 30 days of cold exposure (4‡C) when using hexobarbital as a substrate. In fasted animals the cold-acclimated rats showed higher levels of hexobarbital metabolic rates compared to control rats, but there was no significant difference in fed animals. The maximum rates of hexobarbital metabolism produced by xylitol perfusion were also significantly higher in the perfused liver of cold-acclimated rats. It was concluded that the function of the cytochrome P-450 system for hexobarbital in cold-acclimated rats changed due to both an increase in the activity of the cytochrome P-450 system and to changes in regulation of the cytochrome P-450 system by the supply of reducing equivalents. © 1986 Swets & Zeitlinger.

Interaction of Trichloroethane Isomers with Cytochrome P-450 in the Perfused Rat Liver. TAKANO, T., MIYAZAKI, Y., and MOTOHASHI, Y. (1985). Fundam. Appl. Toxicol. 5, 353-360. The real-time interactions of 1,1,1-trichloroethane (TCE) and 1,1,2-TCE with cytochrome P-450 were observed using in vivo optical methods to measure the spectral changes of cytochrome P-450 and the reduction-oxidation transition of pyridine nucleotides in the perfused liver of rats treated with phenobarbital. Changes in oxygen consumption and TCE uptake were also measured. The spectral changes of cytochrome P-450 indicated that both TCE isomers bound to low spin (substrate free) ferric cytochrome P-450 and formed a high spin (substrate complexed) form. However, 1,1,1-TCE bound more tightly to cytochrome P450 and seemed to be only slowly metabolized compared to 1,1,2-TCE. The stoichiometry of the change in oxygen consumption rate to the change in 1,1,1-TCE uptake rate ranged between 5/1, and 9/1, whereas that of 1,1,2-TCE was 1.4 to 2.0. Decreases in reduced pyridine nucleotides associated with TCE administration were significantly larger with 1,1,1-TCE than with 1,1,2-TCE. The inhibitory effect of 1,1,1-TCE on hexobarbital metabolism in the perfused liver was greater than that of 1,1,2-TCE. Considering our previous data indicating that TCE did not stimulate mitochondrial respiration, it is postulated that the far higher amount of oxygen consumption associated with the binding of 1,1,1-TCE to cytochrome P450 than the amount which was necessary to mixed-function oxidation of this compound was due to an uncoupling effect of 1,1,1 -TCE on the mixed-function oxidase system. © 1985 Copyright 1985 by the Society of Texicology.

©, The interaction of carbon monoxide (CO) with cytochrome P‐450 associated with hexobarbital metabolism was observed in hemoglobin‐free perfused rat liver by using a scanning reflectance spectrophotometer. The evidence obtained showed that CO bound to the substrate complexed cytochrome P‐450 and, at a CO/O2 ratio of over 0.1 in the perfusate, inhibited the hexobarbital metabolism estimated from the hexobarbital uptake, and oxygen consumption. Although the oxygen supply to the liver cell was one of the major limiting factors during CO hypoxia, CO binding to cytochrome P‐450 significantly enhanced the suppression of hexobarbital oxidation caused by hypoxic hypoxia.

The combined effects of nitrogen dioxide (NO2) and cold stress were assessed on the cytochrome P-450 system by measuring microsomal protein content, cytochrome P-450 content, aminopyrine activity, and aniline hydroxyalse activity in the liver of male Wistar rats exposed to 4 ppm NO2 and/or environment (4°C) for 24 h, 14 days,a nd 30 days. Exposure to cold alone changed the activity of the cytochrome P-450 system during the exposure up to 30 days,a nd exposure to NO2 alone also infleunce it after 14 days and 30 days of exposure. Interaction were observed in the effect on the cytochemical P-450 system when rats exposed to NO2 and cold simultaneously. There was a tendency that NO2 suppressed the increased in activities of the cytochrome P-450 system caused by cold of 24-h and 30-day exposure. © 1984.

To investigate the effects of heat and exercise on firefighters wearing anti-fire coat, following measurements were made using five healthy untrained male subjects at rest and during exercise in a hot environment. The physiological parameters were loss of weight, axillary temperature, respiratory rate, ventilation, oxygen consumtion, carbon dioxide output, blood pressure, heart rate. The hematological parameters were red blood cell counts, white blood cell counts, and their differential. The blood biochemical parameters were osmolarity, Na, K, Cl, total protein, total cholesterol, free fatty acids, glucose, lactate, pyruvate, CPK, CPK isozyme, LDH, GOT, aldolase, creatinine, creatine, myoglobin, and those for urine were osmolarity, Na, K, Cl, urea nitrogen, creatinine, creatine, myoglobin. Two separate experiments were conducted as follows: sitting for 30 minutes in climatic chamber at 25°C, 35°C, 45°C and 55°C respectively with the relative humidity at about 40% and during exercise in the chamber at 25°C and 50°C with the relative humidity at about 40% for 20 minutes, including 10 minutes exercise with a bicycle ergometer at 600kpm/min followed by 10 minutes rest. Serum and urinary myoglobin were assayed by the radioimmunoassay method.<br>The degree of weight loss and increase in heart rate and serum enzyme activities were more significant when the subjects wore the anti-fire coat than when they were naked. GOT, LDH, CPK and serum myoglobin significantly increased after exercise at 50°C, but not after exercise at 25°C or at rest in 50°C temperatures. The results thus indicate that the effects of the combination of heat and exercise were greater than the sum of their individual effects.<br>It was concluded that heat stagnation must be taken into consideration, given the work condition and anti-fire coat worn by firefighters.

©, To study the combined effect of nitrogen oxides (NOx) and cold stress on circulating leukocyte counts, the numbers of total leukocytes, neutrophils, lymphocytes, and eosinophils were counted in rats after 3 h exposure to NOx and/or cold stress. There was a tendency for both NOx and cold stress to increase the total leukocyte count and the neutrophil count, and to decrease the eosinophil count. The data indicated that the effects of NOx and cold stress were additive when they acted simultaneously.

To study the combined effect of nitrogen oxides (NOx) and cold stress on circulating leukocyte counts, the numbers of total leukocytes, neutrophils, lymphocytes, and eosinophils were counted in rats after 3 h exposure to NOx and/or cold stress. There was a tendency for both NOx and cold stress to increase the total leukocyte count and the neutrophil count, and to decrease the eosinophil count. The data indicated that the effects of NOx and cold stress were additive when they acted simultaneously. © 1983.

The cerebral and cerebellar lesions of the cats that were exposed to 0.3% carbon monoxide gas under artificial respiration were examined by electron microscope at different intervals. During the first few days, the most outstanding features were segmental empty axonal swelling, dilatation of the extracellular space, swelling and necrosis of astrocytes and oligodendroglias, and lamellar separation of the myelin sheath predominantly in the deep cerebral white manner. These changes subsided within one week. Instead, collapsed myelin increased in number and phagocytosis of disintegrated myelin was occasionally observed. Astrocytes and oligodendroglias became prominent in size and number. Changes suggestive of selective damage of myelin or oligodendroglia was not encountered. We proposed that CO-induced experimental cerebral damage may be fundamentally an axonal injury followed by Wallerian degeneration. The pathogenesis of Co-encephalopathy is also discussed.

For all members of the chlorinated ethane and ethylene series except monochloroethylene, the effects on the oxygen consumption of isolated rat mitochondria were studied. All the tested compounds inhibited glutamate and malate oxidation, and their inhibitory potency increased in the order of the number of contained chlorines. The eight compounds of greatest potency were also investigated for their inhibition of succinate oxidation in mitochondria and inhibition of NADH oxidation of sonicated submitochondrial particles. The data obtained suggested that the inhibition of substrate oxidation was due to blockade of electron transport and the most susceptible portion was located from NADH to CoQ.

©, The direct effects of carbon monoxide (CO) on cardiac function were investigated in hemoglobin-free living rabbits treated with perfluorochemical blood substitutes. After exchange transfusion with a perfluorochemical emulsion, the erythrocyte count was below 10 x 104/mm3 in each animal. Gas mixtures of oxygen with 5%, 10%, and 20% of CO or nitrogen were administered via a respirator. The results showed that the cardiac effects of CO and nitrogen were significantly different as regards changes in arterial pressure, pulse pressure, heart rate, and the product of heart rate and systolic arterial pressure in spite of the same oxygen tension in the inhaled gases. It was concluded that there was a direct effect of CO not mediated by hemoglobin.

Experimental studies were performed to elucidate the significance of various physiological factors contributing to the pathogenesis of carbon monoxide (CO) encephalopathy, such as systemic blood pressure (BP), common carotid artery blood flow (CF), local blood flow (LBF) of the brain and blood gas including pH, and to analyse the morphological character of the cerebral white matter lesions in the acute phases with light and electron microscopes; 14 adult cats were exposed to 0.3% CO/air gas under respiratory control for 1 h and 17 min to 2 h and 50 min and killed 1.5 h to 3 weeks later. During the 1st h the CF and LBF increased along with the concentration of CO haemoglobin and the BP showed slight decrease in all the CO-exposed cats. After the 1st h, the BP dropped progressively as well as the CF and LBF. The LBF of the cortex and white matter changed in parallel, but often that of the latter approximated or exceeded that of the former in the cerebrum. During CO exposure, acidosis occurred in all the cats and haemoconcentration resulted in almost all of the cats. In all the cats except one which showed the least BP drop, lesions occurred selectively in the cerebral white matter and in six or seven cats focal coagulation necrosis or ischaemic changes occurred in the nerve cells in the bilateral pallidum, substantia nigra, and hippocampus similar to human patients. The cerebral white matter lesions were suggestive of those caused by circulatory disturbance. The severity of the white matter damage showed a good positive correlation with the intensity of the BP drop, but not with other factors, such as the duration of CO-exposure, CO-haemoglobin level, acidosis, or haemoconcentration. On the basis of such physiological and morphological findings, we have found the following to be essential for the selective damage of the cerebral white matter rather than the cerebral cortex or white matter of other regions of the CNS: (1) the coexistence of the initial phase of increase in and the succeeding decrease in the cerebral blood flow and (2) the anatomical finding that the cerebral white matter is supplied by its own long nourishing arteries with small amounts of capillary beds and a thinner media compared with that of the subarach-noidal artery. © 1981 Springer-Verlag.

To evaluate the efficacy of hyperbaric oxygen on cyanide intoxication, changes in the intracellular oxidation-reduction state of the renal cortex were observed in situ in 16 New Zealand white rabbits by detecting the reduced pyridine nucleotide fluorescence that represents the degree of cyanide blockade of the respiratory chain. The data indicated that 100% oxygen at 2 ATA exerted both prophylactic and therapeutic antagonistic effects on the cyanide poisoning. Administration of hyperbaric oxygen could constitute a significant treatment if proper chemical treatment is carried out concomitantly.