Emi Sasaki

Therapeutic effect of melatonin on carbon tetrachloride-induced acute liver injury in rats

The therapeutic effect of melatonin on acute liver injury was examined in rats intoxicated with carbon tetrachloride (CCl4). Melatonin (10, 50, or 100 mg/kg body weight [BW]) was intraperitoneally administered to male Wistar rats 6 hr after intraperitoneal injection of CCl4 (1.6 g/kg BW) at which time an apparent liver injury occurred. This post‐melatonin administration dose dependently prevented the progression of liver injury at 24 hr after CCl4 injection, judging from the levels of serum transaminases, indices of liver cell damage. Rats injected with CCl4 alone showed an increase in liver lipid peroxide (LPO) content and a decrease in liver reduced glutathione content at 6 and 24 hr after the injection. The post‐melatonin administration dose dependently ameliorated both changes found at 24 hr after CCl4 injection. Rats injected with CCl4 alone showed an increase in liver triglyceride (TG) content and decreases in serum TG concentration and liver tryptophan 2,3‐dioxygenase (TDO) activity, a marker of the inhibition of liver protein synthesis by CCl4, at 6 and 24 hr after the injection, and also a decrease in serum albumin concentration at 24 hr. The changes in serum TG, albumin concentration, liver TG content, and TDO activity found at 24 hr after CCl4 injection were not ameliorated by the post‐administration of melatonin. The same administration of melatonin dose dependently reduced liver LPO content in CCl4‐untreated rats. These results indicate that melatonin exerts a therapeutic effect on CCl4‐induced acute liver injury in rats, possibly through its antioxidant action.

Preventive effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract on the development of stress-induced acute gastric mucosal lesions in rats.

The preventive effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract (TJ-15), a traditional Chinese herbal medicine for the therapies of gastric ulcers and gastritis, on the development of stress-induced acute gastric mucosal lesions was examined in rats with water immersion restraint (WIR) stress. Simultaneous p.o. administration of TJ-15 at a dose of 20, 100 or 250 mg/kg prevented dose-dependently gastric mucosal lesion development in rats subjected to WIR stress over a 6-h period. In the gastric mucosa of rats with WIR stress alone, lipid peroxide concentration and xanthine oxidase (XOD) and myeloperoxidase--an index of neutrophil infiltration--activities increased with lesion development, while nonprotein SH concentration decreased. The simultaneous administration of TJ-15 attenuated all these changes with gastric mucosal lesion development in a dose-dependent manner. These results indicate that simultaneously administered TJ-15 exerts a preventive effect on the development of WIR stress-induced acute gastric lesions in rats, and suggest that the preventive effect of TJ-15 could be due to its preventive actions on enhanced sulfhydryl oxidation and lipid peroxidation via oxygen free radicals generated by the xanthine-xanthine oxidase system and infiltrated neutrophils in the gastric mucosa and on neutrophil infiltration into the tissue.

Protective effect of melatonin against α-naphthylisothiocyanate-induced liver injury in rats

The protective effect of melatonin against α‐naphthylisothiocyanate (ANIT)‐induced liver injury with cholestasis was examined in rats injected once with the toxicant (75 mg/kg body weight (BW)). In rats injected with ANIT alone, liver injury with cholestasis did not occur 12 hr after the injection but appeared at 24 hr, judging from the serum levels of marker enzymes and components. When melatonin (10 or 100 mg/kg BW) was orally administered to the ANIT‐injected rats at 12 hr after the injection, the administered indoleamine dose‐dependently prevented the formation of liver injury with cholestasis. In rats injected with ANIT alone, serum lipid peroxide (LPO) concentration increased 24 hr after the injection, while liver LPO concentration increased 12 hr after the injection and further increased at 24 hr. Myeloperoxidase (MPO) activity, an index of tissue neutrophil infiltration, in the liver of the ANIT‐injected rats increased 12 hr after the injection and further increased at 24 hr. The oral administration of melatonin (10 or 100 mg/kg BW) to the ANIT‐injected rats attenuated the increases in serum and liver LPO concentrations and liver MPO activity found at 24 hr after the injection in a dose‐dependent manner. These results indicate that orally administered melatonin at pharmacological doses protects against ANIT‐induced liver injury with cholestasis in rats, and suggest that this protective effect of melatonin could be due to its antioxidant action and its inhibitory action against neutrophil infiltration in the liver of ANIT‐injected rats.

An association between lipid peroxidation and α-naphthylisothiocyanate-induced liver injury in rats

An association between lipid peroxidation and alpha-naphthylisothiocyanate (ANIT)-induced liver injury was examined in rats injected once with the toxicant (75 mg/kg body weight). The severity of liver injury was estimated 12, 24, 48, and 72 h after ANIT injection. Liver injury appeared 24 h after ANIT injection, progressed at 48 h, and recovered at 72 h, judging from the serum levels of marker enzymes and components. Serum lipid peroxide (LPO) concentration increased 24 h after ANIT injection and further increased at 48 h, but this increase was attenuated at 72 h. In contrast, liver LPO content increased 12 h after ANIT injection and further increased 24 and 48 h, but this increase was attenuated at 72 h. Similarly, myeloperoxidase (MPO) activity, an index of neutrophil infiltration, in the liver tissue increased 12 h after ANIT injection and further increased at 24 and 48 h, but this increase was attenuated at 72 h. Either serum LPO concentration or liver LPO content was significantly correlated with liver MPO activity (r = 0.661 for serum LPO concentration; r = 0.585 for liver LPO content). These results suggest that lipid peroxidation might be associated with ANIT-induced liver injury in rats and that this lipid peroxidation might occur via oxygen radicals derived from neutrophils infiltrated into the liver tissue of ANIT-intoxicated rats.

Change in hepatic antioxidant defense system with liver injury development in rats with a single α-naphthylisothiocyanate intoxication

The change in hepatic antioxidant defense system with the development of alpha-naphthylisothiocyanate (ANIT)-induced liver injury was examined in rats injected once with the toxicant (75 mg/kg body weight). Liver injury with cholestasis did not occur 12 h after ANIT injection, but appeared at 24 h, progressed at 48 h, and recovered at 72 h, judging from the serum levels of marker enzymes and components. Liver lipid peroxide content increased 12 h after ANIT injection and further increased 24 and 48 h, but this increase was attenuated at 72 h. Liver superoxide dismutase and catalase activities decreased 24 and 48 h, respectively, after ANIT injection, although the catalase activity increased at 12 h, but these decreases were attenuated at 72 h. Liver Se-glutathione peroxidase activity remained unchanged 24, 48, and 72 h after ANIT injection, although the activity increased at 12 h. Liver reduced glutathione content increased 24 h after ANIT injection, but the increase was reduced time dependently thereafter. Liver ascorbic acid content increased 12 h after ANIT injection and further increased at 24 h, but the increase was reduced time dependently thereafter. These results indicate that the change in hepatic antioxidant defense system occurs before and with the development of ANIT-induced liver injury in rats, and suggest that the reduction of hepatic antioxidant defense system mediated by SOD and catalase could contribute to the liver injury development through an enhancement of hepatic lipid peroxidation.

Inhibitory effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract on hepatic triglyceride accumulation with the progression of carbon tetrachloride-induced acute liver injury in rats

The inhibitory effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract (TJ-15) on hepatic triglyceride (TG) accumulation with the progression of acute liver injury was examined in rats intoxicated with carbon tetrachloride (CCl4). TJ-15 at a dose of 100, 250 or 500 mg/kg body weight (BW) was orally administered to male Wistar rats aged 7 weeks, 6 h after the intraperitoneal injection of CCl4 (1.0 ml/kg BW) at which time apparent liver injury and hepatic TG accumulation occurred. TJ-15 significantly prevented not only the progression of liver injury but also inhibited hepatic TG accumulation with the progression of the injury in a dose-dependent manner when these effects were examined 24 h after CCl4 injection. In CCl4-untreated rats with oral administration of TJ-15 at a dose of 100, 250 or 500 mg/kg BW, liver and serum TG concentrations decreased depending on the dose of the herbal medicine. These results indicate that in rats intoxicated once with CCl4, orally administered TJ-15 can inhibit hepatic TG accumulation with the progression of acute liver injury by its decreasing action on serum and liver TG levels, leading to a prevention of the progression of the liver injury.

Preventive Effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) Extract on Progression of Carbon tetrachloride-induced Acute Liver Injury in Rats

The effect of oral administration of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract (TJ-15) on the progression of acute liver injury was examined in rats intoxicated with carbon tetrachloride (CCl4). When TJ-15 at a dose of 500 mg/kg body weight (b.w.) was administered to male Wistar rats aged seven weeks 6 hours after i.p. injection of CCl4 (1.0 ml/kg b.w.), an apparent liver injury occurred. Significant prevention against the progression of liver injury was found 24 hours after the injection judging from the activities of serum transaminases and other indices of liver cell damage. An increase in lipid peroxide level and decreases in reduced glutathione level and superoxide dismutase (SOD) activity occurred in the liver at 6 and 24 hours after CCl4 injection. Serum SOD activity increased 24 hours after CCl4 injection. Post-oral TJ-15 administration significantly ameliorated all these changes found at 24 hours after CCl4 injection. An increase in liver triglyceride level and a decrease in serum triglyceride level also occurred 6 and 24 hours after CCl4 injection. Post-oral TJ-15 administration prevented the increase in liver triglyceride level at 24 hours after CCl4 injection. Although the activity of liver tryptophan 2,3-dioxygenase (TDO), a marker of the inhibition of liver protein synthesis by CCl4, decreased 6 and 24 hours after injection of the toxicant, post-oral TJ-15 administration had no effect on this decrease in TDO activity at 24 hours after the injection. These results indicate that oral TJ-15 administration can prevent the progression of acute liver injury in CCl4-injected rats, and suggest that this prevention could be due to the action of TJ-15 to scavenge free radicals formed in the liver and to inhibit triglyceride accumulation in the liver.

Contribution of the antilipid peroxidative action of Dai-saiko-to extract to its preventive effect on carbon tetrachloride-induced acute liver injury in rats

Post‐oral administration of Dai‐saiko‐to extract (TJ‐8), a traditional herbal medicine, ameliorated acute liver injury in rats intoxicated with carbon tetrachloride (CCl4). This TJ‐8 administration inhibited an increase in lipid peroxide contents in the liver homogenate and microsomal fraction and a decrease in glucose‐6‐phosphatase activity in the liver microsomal fraction, an index of lipid peroxidation‐mediated damage in liver microsomes, during the progression and recovery of the liver injury. These results indicate that the antilipid peroxidative action of TJ‐8 contributes to its preventive effect on CCl4‐induced acute liver injury in rats.

Preventive effect of dai-saiko-to (da-chai-hu-tang) extract on disrupted hepatic active oxygen metabolism in rats with carbon tetrachloride-induced liver injury.

In order to clarify the preventive action of Dai-Saiko-to (Da-Chai-Hu-Tang) extract (TJ-8) on the progression of acute liver injury in rats intoxicated with carbon tetrachloride (CCl4), we examined the effect of post-oral TJ-8 administration on hepatic active oxygen metabolism following the progression of this liver damage. When TJ-8 (1.0 g/kg body weight) was administered orally to male Wistar rats aged five weeks 2 hrs after i.p. injection of CCl4 (1.0 ml/kg body weight), an apparent liver injury occurred. Significant prevention against the progression of liver injury was found at 24 hrs after injection, judging from the activities of serum transaminases, indexes of liver cell damage. Liver cytosolic superoxide dismutase (SOD) activity decreased 2 and 24 hrs after CCl4 injection, while liver cytosolic catalase and glutathione reductase (GSSG-R) activities decreased 24 hrs after the injection. At 2 and 24 hrs after CCl4 treatment, liver cytosolic Se-containing glutathione peroxidase (GSH-px) activity did not change and liver cytosolic glucose-6-phosphate dehydrogenase (G-6-PDH) activity increased. Post-oral TJ-8 administration significantly ameliorated decreases in liver SOD, catalase, and GSSG-R activities at 24 hrs after CCl4 injection, but did not affect liver Se-GSH-px and increased liver G-6-PDH activities at 24 hrs after the injection. Although increased liver lipid peroxide level and decreased liver reduced glutathione and ascorbic acid levels were observed 2 and 24 hrs after CCl4 injection, post-oral TJ-8 administration significantly prevented these changes found at 24 hrs after injection. These results indicate that post-oral TJ-8 administration can prevent the progression of acute liver injury in CCl4-injected rats by inhibiting enhanced lipid peroxidation and by improving disrupted active oxygen metabolism in the injured liver.

Characterization of the L-tryptophan transport system in the liver of growing rats

In order to characterize the system of L-tryptophan (TRP) transport into liver during the growing period of 10 to 42 days, the changes of tryptophan 2,3-dioxygenase (TDO) activity, levels of serum, liver, brain, and muscle TRP, and the rate and mode of TRP uptake into isolated hepatocytes were examined in male Wistar rats. Liver TDO activity increased rapidly at 16 days of age. A marked and rapid decrease in free serum TRP level occurred before weanling, while a small decrease in total serum TRP level was found after weanling. The change of liver TRP level was similar to that of free serum TRP level and correlated well. There was a significant inverse correlation between liver TDO activity and either free serum TRP level or liver TRP level. A rapid change in TRP level did not occur in brain and muscle during the growing period. The concentrations of brain and muscle TRP correlated better with those of total serum TRP than with those of free serum TRP. The rate of TRP uptake into hepatocytes isolated from rats aged 10 days was lower than that from rats aged 21 and 42 days. The former hepatocytes were lacking in a high-affinity saturable transport component for TRP uptake which was present in the latter ones. The present results indicate that a great change in the system of TRP transport into liver occurs in growing rats, and that in suckling rats a high level of free serum TRP contributes to the efficient transport of the amino acid into the liver.