Ikumi Yonekura

Ethanol-induced enhancement of trichloroethylene metabolism and hepatotoxicity: Difference from the effect of phenobarbital

Male Wistar rats pretreated with ethanol (2.0 g in 80 ml liquid diet/day for 3 weeks) or phenobarbital (PB, 80 mg/kg/day ip for 4 days) were exposed by inhalation to 500, 1000, 2000, 4000, or 8000 ppm trichloroethylene (TRI) for 2 or 8 hr, and the blood concentration of TRI and the urinary concentration of TRI metabolites (trichloroethanol (TCE) and trichloroacetic acid (TCA] were determined at various times. Plasma glutamic-pyruvic transaminase (GPT) activity was measured 22 hr after the end of exposure as an indicator of hepatic damage. Both ethanol and PB enhanced TRI metabolism as evidenced by accelerated disappearance of TRI from the blood and increased excretion of total trichloro compounds (TCE + TCA) in the urine. However, the effects of ethanol and PB were different from each other: ethanol markedly enhanced the metabolism particularly at TRI concentration of 2000 ppm or lower, whereas PB enhanced it only at 4000 ppm or higher. This difference was also reflected in the effect of TRI on liver: ethanol potentiated TRI hepatotoxicity more markedly than did PB when TRI concentration remained 2000 ppm or lower, whereas PB potentiated the toxicity more markedly than ethanol when the concentration was 4000 ppm or higher. It is noteworthy that ethanol potentiated TRI hepatotoxicity at a TRI concentration as low as 500 ppm. The severity of hepatic damage expressed by plasma GPT activity essentially paralleled the urinary excretion rate of total trichloro compounds during and 4 hr after exposure (r = 0.87 to 0.93). Compared between the contribution of concentration and duration of exposure to the toxicity, a higher concentration of TRI tended to cause more severe liver damage to PB-treated rats than did a prolonged period of exposure, whereas the toxicity in ethanol-treated rats was generally more marked in rats exposed to TRI for a longer period than in rats exposed to a higher concentration.

Effects of ethanol and phenobarbital administration on the metabolism and toxicity of benzene.

Effects of ethanol- and phenobarbital(PB)-treatment on the metabolism of benzene in vitro and in vivo, and on the benzene-induced hemotoxicity, were investigated. Ethanol consumption markedly enhanced in vitro metabolism of both benzene and phenol in rat liver, whereas PB-treatment, which enhanced the metabolism of phenol to some degree (about one-third of ethanol-induced enhancement), did not affect the metabolism of benzene. In a single exposure experiment with rats, ethanol increased benzene metabolism in vivo as evidenced by accelerated disappearance of benzene from the blood as well as by elevated urinary excretion of phenol, whereas PB produced little or no significant influence on the metabolism. In a 3-week exposure experiment, ethanol administration accelerated benzene disappearance from the blood in agreement with the single exposure experiment, but it tended to decrease urinary phenol excretion with repetition of exposure, probably due to concomitant stimulation of subsequent phenol metabolism by ethanol. Again, PB-treatment produced only a negligible effect on the metabolism of benzene. Ethanol consumption aggravated benzene-induced hemopoietic disorder as evidenced by a marked decrease in the peripheral white blood cell number. PB produced a protective effect on the toxicity. It is concluded that ethanol potentiates benzene toxicity by accelerating (1) hydroxylation of benzene, a rate-limiting step of benzene metabolism and (2) transformation of phenol into highly toxic metabolites.

Effects of carbohydrate intake on the blood ethanol level and alcoholic fatty liver damage in rats

Effects of carbohydrate (CHO) intake on the blood ethyl alcohol (ethanol) level were studied in rats with a surgically placed gastric cannula. A basal diet (protein, 2.07; fat, 1.98; CHO, 5.76 g/day), a high-CHO diet (CHO, 4.39 g/day) + ethanol, a medium-CHO diet (CHO, 2.69 g/day) + ethanol or a low-CHO diet (CHO, 0.98 g/day) + ethanol was infused into the stomach for 4 weeks starting from the 2nd postoperative week. The basal diet and the test diets were isocaloric, and the ethanol (2.80 g/day) in the test diets accounted for 39% of the total calories. The liquid diets (50 kcal in 50 ml) were infused over 16 h from 16.00 to 08.00 h each day. The low-CHO diet group had significantly higher blood ethanol levels than the high-CHO diet group 4, 8 and 16 h after the start of infusion. These groups could be ranked by liver triglyceride content at autopsy as follows: low-CHO > medium-CHO > high-CHO > or = basal. Consistent with the triglyceride content, histological changes of the liver could be ranked by the degree of fatty changes in the same order: low-CHO > medium-CHO > high-CHO > basal. Thus, for a given amount of ethanol consumption, lower CHO intake was associated with higher blood ethanol levels and with more severe fatty changes of the liver.

Ethanol ingestion combined with lowered carbohydrate intake enhances the initiation of diethylnitrosamine liver carcinogenesis in rats

The effect of ethanol on the initiation of diethylnitrosamine- (DEN) induced liver carcinogenesis was investigated in rats. In the first experiment, eight-week-old male Wistar rats were maintained on four liquid diets: a basal diet (Group 1), a low-carbohydrate (low-CHO) diet (Group 2), a basal diet+ethanol (Group 3), or a low-CHO diet+ethanol (Group 4). After three weeks on these diets, 50 mg/kg of DEN was injected intraperitoneally. The plasma glutamic-oxaloacetic transaminase activity in Group 4 was higher 24 hours after DEN administration than in Groups 1 and 3. The plasma glutamic-pyruvic transaminase activity in Groups 3 and 4 was higher than in Groups 1 and 2. The number of gamma-glutamyltranspeptidase-positive foci per unit liver area 41 weeks after DEN administration was higher in Group 4 than in Group 1. The area of gamma-glutamyltranspeptidase-positive foci was greater in Groups 2 and 4 than in Group 1. In the second experiment, Groups 1 and 4 were given DEN orally (25 or 75 mg/kg). Plasma glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase activities 24 hours after DEN administration were significantly higher in Group 4 than in Group 1, but only when the dose of DEN was 75 mg/kg. In contrast, the number and area of placental glutathione S-transferase-positive foci per unit liver area were greater in Group 4 than in Group 1 only after 25 mg/kg of DEN. Thus the severity of hepatotoxicity and the incidence of precancerous liver lesions were not necessarily correlated. These findings together indicate that a combination of ethanol and a low-CHO diet enhances DEN-induced liver carcinogenesis in rats by increasing the bioactivation of DEN in the liver.

Survey of Resistance to Metals and Volatilization Activity of Hg-Resistant R Plasmids in Citrobacter Isolated from Clinical Lesions in Japan

Clinical isolates of Citrobacter (277 strains) were studied for the resistance to four metals and four drugs. The distribution patterns of their susceptibility to Hg, Cd and As clearly revealed two peaks, but only a single peak of resistance to Pb. The frequencies of resistance to Hg, Cd, As, SM, TC, CP and KM were 31.8, 94.2, 57.8, 51.3, 44.8, 35.7 and 28.9%, respectively. And we selected 88 mercury resistant strains, and they were tested for their ability to transfer the resistance to the mercury and drug sensitive recipients of E. coli K12-ML1410-Nx and E. coli JE17-Rif. Among 88 strains of Hg resistant Citrobacter, 80 R plasmids with Hg resistance could be demonstrated. It should be noted that transferable R plasmids with Hg resistance were demonstrated in 91% of the Hg-resistant isolates. Furthermore, we tested the volatilization of mercury by strains containing these mercury resistance plasmids, by using radioactive 203Hg2+. All of these isolates of Citrobacter have volatilization activity of Hg2+. Also, all of these volatilization activity is inducible.

Benzethonium Chloride Resistance in Pseudomonas aeruginosa Isolated from Clinical Lesions

The benzethonium chloride resistance of 341 strains of Pseudomonas aeruginosa isolated from Jikei University Hospital was determined. The distribution pattern of the susceptibility to benzethonium chloride clearly revealed two peaks, and the resistance was differentiated by 1000 micrograms/ml (0.1%) of benzethonium chloride. The frequency of resistance to benzethonium chloride was 51.6%. Furthermore, the frequencies of resistance to SM, TC, CP, KM, GM, PIP, Hg, Cd, As and chlorhexidine were 42.5, 15.8, 41.3, 29.6, 14.0, 8.2, 88.3, 97.9, 97.1, and 74.5%, respectively.