• Journal of Nutrition and Health
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• v.24 no.6
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• pp.485-495
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• 1991

Using isolated perfused livers obtained from rats that have been fed saturated and unsatu-rated fatty acid diets the rates of hepatic microsomal oxidation of 7-ethoxycoumarin(EC) to 7-hydroxycoumarin(HC) and the rates of subsequent conjugation of the produced HC to its glucuronide and sulfate esters have been determined. Prior to preparing the isolated perfused livers. rats were fed either fat free diet 10% beef tallow diet or 10% corn oil diet for 3 weeks. The rates of oxidation from EC to HC and also of the subsequent glucuronidation of HC were higher in the corn oil diet group than those found for the fat free and beef tallow diet groups. When the concentrations of infusing EC were increased stepwise there was a dose-dependnet increase for the release of the glucuronide form of HC metabolites at the expense of the sulfate ester form. This dose dependant shift observed for the corn oil group was more significnat than those found for other groups. These results indicate that corn oil feeding has produced enhancement in the rates of hepatic microsomal drug oxidation and glucuronide conjugation the reactions catalyzed by enzymes embedded in the hepatic microsomal membranes.

• Biomolecules & Therapeutics
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• v.11 no.3
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• pp.163-168
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• 2003

Pharmacokinetics of eupatilin (an active components of $Stillen^{\circledR}$, a new antigastritic agent) were investigated after both intravenous and oral administration at a dose of 30mg/kg to rats. After intravenous administration, the plasma concentrations of unchanged eupatilin declined rapidly with a mean terminal half-life of 0.101 h. Eupatilin was eliminated fast in rats; the total body clearance was 121 mL/min/kg. Eupatilin was mainly metabolized in rats; the percentage of intravenous dose of eupatilin excreted in 24 h urine and feces as unchanged eupatilin was only 2.5 and 0.919％, respectively. Eupatilin was mainly metabolized to form its glucuronide conjugate; after intravenous administration, 15.9 and 51.7％ of intravenous dose was excreted in 24 h urine and feces, respectively, as eupatilin plus its glucuronide. After oral administration, the absolute bioavailability was only 3.86％ based on $AUC_{0-24h}$ of eupatilin plus its glucuronide. Approximately 68.5％ of oral dose was not absorbed from the entire gastrointestinal tract. Therefore, it could be concluded that the superior effect of eupatilin in experimental animal models of gastric ulcer and inflammatory bowel disease after oral administration could be due to the local action of eupatilin. Further pharmacokinetic studies to elucidate the local action of eupatilin are required.

• Mass Spectrometry Letters
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• v.9 no.1
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• pp.24-29
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• 2018

DC23, a triazolothione resorcinol analogue, is known to inhibit heat shock protein 90 and pyruvate dehydrogenase kinase which are up-regulated in cancer and diabetes, respectively. This study was performed to elucidate the metabolism of DC23 in human liver microsomes (HLMs). HLMs incubated with DC23 in the presence of uridine 5'-diphosphoglucuronic acid (UDPGA) and/or ${\beta}$-nicotinamide adenine dinucleotide phosphate (NADPH) resulted in the formation of four metabolites, M1-M4. M1 was identified as DC23-N-Oxide, on the basis of LC-MS/MS analysis. DC23 was further metabolized to its glucuronide conjugates (M2, M3, and M4). In vitro metabolic stability studies conducted with DC23 in HLMs revealed significant glucuronide conjugation with a $t_{1/2}$ value of 1.3 min. The inhibitory potency of DC23 on five human cytochrome P450s was also investigated in HLMs. In these experiments, DC23 inhibited CYP2C9-mediated tolbutamide hydroxylase activity with an $IC_{50}$ value of $8.7{\mu}M$, which could have implications for drug interactions.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.5
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• pp.591-595
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• 1997

An ex vivo assay determining the flavin-containing monooxygenase (FMO) activity in perfused rat liver has been developed by assessing the rate of thiobenzamide S-oxide (TBSO) formation from the infused thiobenzamide (TB). The hepatotoxicity by TB or TBSO was not a critical factor for maintaining the FMO activity for up to 50 min. The FMO activity expressed in nmoles TBSO produced/g liver/min was the same for the recycling and non-recycling perfusion. This implies that reduction of the oxidized TBSO back to the parent compound (TB) is negligible. Hydrolysis of the collected perfusates with either ${\beta}-glucuronidase$ or arylsulfatase did not increase the TBSO level and thus, TBSO does not appear to undergo conjugation either to glucuronide or sulfate esters. Thus, measuring the rate of TB S-oxidation in the isolated perfused liver with 1 mM TB for 50 min provides a useful tool for evaluation of the hepatic FMO activity in the absence of hepatic necrosis and without the interferences caused by further conjugation or back reduction of the TBSO to the parent TB.

• Journal of Microbiology and Biotechnology
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• v.33 no.10
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• pp.1351-1360
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• 2023

Endocrine-disrupting chemicals (EDCs) are compounds that disturb hormonal homeostasis by binding to receptors. EDCs are metabolized through hepatic enzymes, causing altered transcriptional activities of hormone receptors, and thus necessitating the exploration of the potential endocrine-disrupting activities of EDC-derived metabolites. Accordingly, we have developed an integrative workflow for evaluating the post-metabolic activity of potential hazardous compounds. The system facilitates the identification of metabolites that exert hormonal disruption through the integrative application of an MS/MS similarity network and predictive biotransformation based on known hepatic enzymatic reactions. As proof-of-concept, the transcriptional activities of 13 chemicals were evaluated by applying the in vitro metabolic module (S9 fraction). Identified among the tested chemicals were three thyroid hormone receptor (THR) agonistic compounds that showed increased transcriptional activities after phase I+II reactions (T3, 309.1 ± 17.3%; DITPA, 30.7 ± 1.8%; GC-1, 160.6 ± 8.6% to the corresponding parents). The metabolic profiles of these three compounds showed common biotransformation patterns, particularly in the phase II reactions (glucuronide conjugation, sulfation, GSH conjugation, and amino acid conjugation). Data-dependent exploration based on molecular network analysis of T3 profiles revealed that lipids and lipid-like molecules were the most enriched biotransformants. The subsequent subnetwork analysis proposed 14 additional features, including T4 in addition to 9 metabolized compounds that were annotated by prediction system based on possible hepatic enzymatic reaction. The other 10 THR agonistic negative compounds showed unique biotransformation patterns according to structural commonality, which corresponded to previous in vivo studies. Our evaluation system demonstrated highly predictive and accurate performance in determining the potential thyroid-disrupting activity of EDC-derived metabolites and for proposing novel biotransformants.

• Archives of Pharmacal Research
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• v.23 no.6
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• pp.620-625
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• 2000

The mechanisms of liver injury from cold storage and reperfusion are not completely under-stood. The aim of the present study was to investigate whether the inactivation of Kupffer cells (KCs) by gadolinium chloride ($GdCl_3$) modulates ischemia-reperfusion injury in the rat liver. Hepatic function was assessed using an isolated perfused rat liver model. In livers subjected to cold storage at $4^{\circ}C$ in University of Wisconsin solution for 24 hrs and to 20 min rewarm-ing ischemia, oxygen uptake was markedly decreased, Kupffer cell phagocytosis was stimulated, releases of purine nucleoside phosphorylase and lactate dehydrogenase were increased as compared with control livers. Pretreatment of rats with $GdCl_3$) , a selective KC toxicant, suppressed kupffer cell activity, and reduced the grade of hepatic injury induced by ischemia-reperfusion. While the initial mixed function oxidation of 7-ethoxycoumarin was not different from that found in the control livers, the subsequent conjugation of its meta-bolite to sulfate and glucuronide esters was suppressed by ischemia-reperfusion, CdCl$_3$restored sulfation and glucuronidation capacities to the level of the control liver. Our findings suggest that Kupffer cells could play an important role in cold/warm ischemia-reperfusion hepatic injury.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.2
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• pp.261-269
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• 1998

Concomitant administration of a single acute dose of ethanol (4 g/kg) protected mice from the hepatocellular injury observed upon administration of a large dose of acetaminophen (400 mg/kg). This was evidenced by the normal histological appearances of liver sections and by the lowered serum aminotransferase activities in mice treated with ethanol and acetaminophen together. In the mice treated with acetaminophen alone, along with the hepatic necrosis, the hepatic microsomal aminopyrine N-demethylase activity was decreased. However, co-administration of ethanol prevented this acetaminophen dependent inhibition on the microsomal mixed function oxidase activity. Pharmacokinetic studies indicated that the concentration of un-metabolized drug in the blood was increased in the ethanol treated mice. Furthermore, upon co-administration of ethanol, although the biliary levels of acetaminophen metabolites (glucuronide, sulfate and cysteine conjugates) were decreased, the level of unmetabolized acetaminophen was increased. Our findings suggest that co-administration of an acute dose of ethanol reduces the degree of hepatocellular necrosis produced by a large dose of acetaminophen and this ethanol dependent protection is, in major part, afforded by suppression of the hepatic microsomal mixed function oxidase activity catalyzing the metabolic activation of acetaminophen.

• Proceedings of the Korean Society of Food Science and Nutrition Conference
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• 2004.11a
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• pp.65-70
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• 2004

Modulation of biotransformation enzymes is one mechanism by which a diet high in fruits and vegetable may influence cancer risk. Inhibition of cytochrome P450s (CYP) and concomitant induction of conjugating enzymes are hypothesized to reduce the impact of carcinogens in humans. Thus, exposure to types and amounts of phytochemicals may influence disease risk. Like other xenobiotics, many classes of phytochemicals are rapodly conjugated with glutathione, glucuronide, and sulfate moieties and excreted in urine and bile. In humans, circulating phytochemical levels very widely among individuals even in response to controlled dietary interventions. Polymorphisms in biotransformation enzymes, such as the glutathione S-transferases (GST), UDP-glucuronosyltransferases (UGT), and sulfotransferases (SULT), may ocntribute to the variability in phytochemical clearance and efficacy; polymorphic enzymes with lower enzyme activity prolong the half-lives of phytochmicals in vivo. Isothiocyanates (ITC) in cruciferous vegetables are catalyzed by the four major human GSTs: however reaction velocities of the enzymes differ greatly. In some observational studies of cancer, polymorphisms in the GSTMI and GSTTI genes that result in complete lack of GSTM1-1 protein, respectively, confer greater protection from cruciferous vegetable in individuals with these genotypes. Similarly, we have shown in a controlled dietary trial that levels of GST-alpha-induced by ITC-are higher in GSTMI-null individuals exposed to cruciferous vegetablse. The selectivity of glucuronosyl conjugation of flavonoids is dependent both on flavonoid structure as well as on the UGI isozyme involved in its conjuagtion. The effects of UGI polymorphisms on flavonoid clearnace have not been examind; but polymorphisms affect glucuronidation of several drugs. Given the strong interest in the chemopreventive effects of flavonoids, systematic evaluation of these polymorphic UGTs and flavonoid pharmacokinetics are warranted. Overall, these studies suggest that for phytochemicals that are metabolized by, and affect activity of, biotransformation enzymes, interactions between genetic polymorphisms in the enzymes and intake of the compounds should be considered in studies of cancer risk. Genetic polymorphisms in biotransformation enzymes may account in prat for individual variation in metabolism of a wide range of phytochemicals and their ultimate impact on health.