Study on potential hepatotoxicity of rhein in Rhei Radix et Rhizoma based on liver metabolism / 中国中药杂志

The bilirubin metabolism mediated by the phase Ⅱ metabolizing enzyme UGT1A1 in the liver was evaluated to study the potential hepatotoxicity risk based on investigation on the inhibitory effect of rhein and its metabolites on the UGT1A1 enzyme in Rhei Radix et Rhizoma. Firstly, in vitro liver microsomes incubation was used to initiate the phase Ⅱ metabolic reaction to investigate the inhibitory effect of rheinon UGT1A1 enzyme. Secondly, the phase Ⅰ and phase Ⅱ metabolic reactions were initiated to investigate the hepatotoxicity risk of rhein metabolites. It was found that the rhein and its phase Ⅱ metabolites had no significant inhibitory effect on UGT1A1 enzyme, but its phase Ⅰ metabolites significantly reduced UGT1A1 enzyme activity. Based on the metabolites analysis, it is speculated that the rhein phase Ⅰ metabolite rheinhydroxylate and its tautomers have certain hepatotoxicity risks, while the toxicity risk induced by the prototype and phase Ⅱ metabolites of rheinglucoside, rheinglucuronic acid and rhein sulfate is small.

Glucuronidation is the dominating in-vivo metabolism pathway of herbacetin:elucidation of herbacetin pharmacokinetics after intravenous and oral administration in rats / 中国药理学与毒理学杂志

OBJECTIVE To map a comprehensive metabolic pathway of herbacetin in rats, specifically, to elucidate the biotransformation of herbacetin in vivo and to simultaneously monitor the pharmacokinetic process of both parent drug and its major metabolites. METHODS liquid chromatography/ion trap mass spectrometry (LC/MSn) and ultra-liquid chromatography coupled with mass spectrometry (UPLC/MS) were combined in the current study for qualitative and quantitative determinations of herbacetin and its metabolites in bile, urine and feces after both oral and intravenous administration of herbacetin to rats. Enzyme kinetic studies on the intestinal and hepatic metabolism of herbacetin were further conducted to elucidate metabolic profiles of herbacetin in rat tissues and organs. Additionally, plasma concentration profiles of herbacetin and its metabolites in rats were obtained to characterize the overall pharmacokinetic behavior of herbacetin. RESULTS It was found that herbacetin was excreted primarily from rat urine in the form of glucuronide-conjugations. Subsequent in vitro enzyme kinetic studies and in vivo pharmacokinetic investigations suggested an extensive hepatic metabolism of herbacetin and the high exposure of herbacetin- glucuronides in systemic circulation. The clearance, half- life and bioavailability of herbacetin in rats were determined as (16.4±1.92)mL·kg-1·min-1, (11.9±2.7)min, and 1.32%, respectively. On basis of these findings, a comprehensive metabolic pathway of herbacetin in rats was composed. In addition, a physiology based pharmacokinetic (PBPK) model was successfully developed with the aid of the GastroPlus to simulate the pharmacokinetic process of herbacetin in rats. Application of the PBPK modeling can provide a useful starting point to understand and extrapolate pharmacokinetic parameters among different species, populations, and disease states. CONCLUSION After oral administration, herbacetin was subjected to colonic degradation and extensive first pass metabolism, with glucuronidation as its dominating in vivo metabolic pathway.

Sequential Metabolism Study on Ginkgo Folium Tablet in Digestive System / 中国中医药信息杂志

Objective To investigate dynamic metabolism in vivo of Ginkgo Folium Tablet under the guidance of sequential metabolism thoughts. Methods In situ closed-loop in rats was carried out to study sequential metabolism of Ginkgo Folium Tablet through oral digestive system, namely to investigate and compare the intestinal flora metabolism, the gut wall metabolism and hepatic metabolism, combined with chromatographic fingerprint of blood samples. Results The analysis showed that 12 peaks in Ginkgo Folium Tablet were metabolized by intestinal flora, and 7 peaks generated through the gut wall. Most components of Ginkgo Folium Tablet were metabolized in liver, and 3 original medicine components were directly into the blood. Conclusion This study conducts a qualitative description of metabolism of Ginkgo Folium Tablet in different parts of the oral route, and provides references for the quality control, mechanism explanation and secondary development for Ginkgo Folium Tablet.

Comparison on in vitro hepatic metabolic characteristics of five kinds of alkaloids from Coptis chinensis / 中草药

Objective: To explore the in vitro hepatic metabolic selectivity of five kinds of isoquinoline alkaloids (with the similar structures) from Coptis chinensis in rats. Methods: Using the method of rat in vitro liver microsomes incubation model, the metabolic kinetics parameters Km, Vmax, and CLint for berberine, palmatine, coptisine, epiberberine, and jateorhizine were calculated by observing the influence of incubation time, protein concentration of liver microsomes, and substrate concentration on metabolic characteristics in liver. Results: The difference of in vitro hepatic metabolic kinetics parameters Km and CLint among five kinds of alkaloids from C. chinensis is statistically significant (P < 0.05). Conclusion: There is a significant selectivity in in vitro hepatic metabolism of five kinds of isoquinoline alkaloids from C. chinensis in rats.

Inhibition of rutaecarpine on in vitro hepatic metabolism of five Coptis alkaloids in rats / 中草药

Objective: To investigate the inhibition of rutaecarpine, a main component in Evodiae Fructus, on the hepatic metabolism of five Coptis alkaloids, and to provide the basis for further study of compatibility mechanism between Coptidis Rhizoma and Evodiae Fructus. Methods: Using rat liver microsome incubation method, the inhibition of rutaecarpine on hepatic metabolism of five Coptis alkaloids in vitro was investigated. Results: Rutaecarpine could inhibit the in vitro hepatic metabolisms of coptisine, epiberberine, berberine, palmatine, and jatrorrhizine. The half inhibitory concentration (IC50) was all greater than 50 μmol/L which showed rutaecarpine had a weak inhibition on Coptis alkaloids. The differences of inhibition constant (Ki) were statistically significant (P jatrorrhizine > palmatine > epiberberine > coptisine. Conclusion: The results could provide the basis to learn the major role on the links that Evodiae Fructus acted on Coptis alkaloids and reveal the compatibility mechanism between Coptidis Rhizoma and Evodiae Fructus.

Portal hypertensive response to kinin

Portal hypertension is the most common complication of chronic liver diseases, such as cirrhosis. The increased intrahepatic vascular resistance seen in hepatic disease is due to changes in cellular architecture and active contraction of stellate cells. In this article, we review the historical aspects of the kallikrein-kinin system, the role of bradykinin in the development of disease, and our main findings regarding the role of this nonapeptide in normal and experimentalmodels of hepatic injury using the isolated rat liver perfusion model (mono and bivascular) and isolated liver cells. We demonstrated that: 1) the increase in intrahepatic vascular resistance induced by bradykinin is mediated by B2 receptors, involving sinusoidal endothelial and stellate cells, and is preserved in the presence of inflammation, fibrosis, and cirrhosis; 2) the hepatic arterial hypertensive response to bradykinin is calcium-independent and mediated by eicosanoids; 3) bradykinin does not have vasodilating effect on the pre-constricted perfused rat liver; and, 4) after exertion of its hypertensive effect, bradykinin is degraded by angiotensin converting enzyme. In conclusion, the hypertensive response to BK is mediated by the B2 receptor in normal and pathological situations. The B1 receptor is expressed more strongly in regenerating and cirrhotic livers, and its role is currently under investigation.

Hipertensão portal é a complicação mais comum das doenças crônicas do fígado, tais como cirrose. A resistência intravascular aumentada observada na doença hepática é devida a alterações na arquitetura celular e contração ativa das células estreladas. Neste trabalho revisamos aspectos históricos do estudo do sistema calicreína-cinina e os resultados de nossos estudos do papel deste nonapeptídeo no controle do tono vascular intra-hepático em condições normais e modelos experimentais de agressão hepática usando a perfusão de fígado isolado de rato (mono e bivascular) e células hepáticas isoladas. Nós demonstramos que: 1) o aumento da resistência vascular intrahepática induzido pela bradicinina é mediado por receptores B2, envolve a participação de células endoteliais sinusoidais e células estreladas e não é alterada pela presença de inflamação, fibrose ou cirrose; 2) a resposta hipertensiva induzida pela bradicinina no sistema arterial hepático é cálcio-independente emediada por eicosanóides; 3) bradicinina não tem efeito dilatador na circulação intra-hepática; 4) após exercer efeito vasoconstritor intra-hepático, a bradicinina é degradada pela enzima conversora de angiotensina. Em conclusão, a resposta hipertensiva à bradicinina é mediada pelo receptor B2 em condições normais e patológicas. Receptor B1 é expresso mais fortemente nos fígados em regeneração e cirróticos e seu papel está sob investigação.

Glucose administration inhibits the hepatic activation of gluconeogenesis promoted by insulin-induced hypoglycemia

The activation of hepatic gluconeogenesis in male Wistar adult 6 h fasted rats during insulin-induced hypoglycemia (IIH) was previously demonstrated. In this study, the effects of intraperitoneal (ip) glucose (100 mg/kg) on the activation of liver gluconeogenesis during IIH was investigated. Thus, 6 h fasted rats that received ip regular insulin (1 U/kg) and 30 min later ip saline (Control group) or glucose (Experimental group) were compared. All the experiments were executed 60 min after insulin injection. The glycemia of Control and Experimental groups were not different (P > 0.05). To investigate gluconeogenesis, liver perfusion experiments were performed. The results demonstrated that excepting glycerol, livers from rats which received ip glucose showed lower (P < 0.05) gluconeogenesis from L-alanine, L-glutamine, L-lactate or L-alanine + L-glutamine + L-lactate + glycerol. Therefore, the absence of glucose recovery after the glucose administration was mediated, at least in part, by an inhibition of hepatic gluconeogenesis.

Em estudo recente empregando ratos Wistar com 6 h de privação alimentar demonstramos que ocorre ativação da neoglicogênese hepática durante a hipoglicemia induzida por insulina (HII). Neste estudo, os efeitos da administração intraperitoneal (ip) de glicose (100 mg/kg) sobre a ativação da neoglicogênese hepática durante a HII foi investigada. Assim, ratos com 6 h de privação alimentar que receberam insulina regular ip (1 U/kg) e 30 min depois salina (Grupo Controle) ou glicose ip (Grupo Experimental) foram comparados. Os experimentos foram executados 60 min após a injeção de insulina. A glicemia dos grupos Controle e Experimental não foi diferente (P > 0.05). Para investigar a neoglicogênese, realizouse experimentos de perfusão de fígado. Os resultados demonstraram, exceto para o glicerol, que fígados de ratos que receberam glicose ip (Grupo Experimental), apresentaram menor taxa (P < 0.05) de neoglicogênese a partir de L-alanina, Lglutamina, L-lactato ou L-alanina + L-glutamina + L-lactato + glicerol. Portanto, a ausência de recuperação da glicemia após administração de glicose foi mediada por inibição da neoglicogênese hepática.