Study the effect of 3,4-Methylenedioxy methamphetamine on cytochrome P450 2E1 activity

Abstract Evaluating the effects of ecstasy on CYP2E1 activity is of great concern, mainly due to growing trends in abuse and co-administration of MDMA with ethanol and the dominant role of this isoenzyme on ethanol metabolism. This study aimed to evaluate the effects of MDMA on CYP2E1 activity. A total of 24 male rats were selected and divided into three groups. The first and second groups consisted of 12 rats and were employed to optimize the perfusion method, and the third group was employed for studying the alteration of CYP2E1 activity after liver exposure to MDMA (300 and 600 ng/ml). The amount of chlorzoxazone and 6-hydroxy chlorzoxazone in a sample obtained from liver perfusion before and after exposure to a buffer containing MDMA was determined by HPLC-FL. The enzymatic activity of rat CYP2E1 decreased after liver perfusion with a buffer containing 600 ng/ml of MDMA. However, no significant changes were observed in chlorzoxazone and 6-hydroxy chlorzoxazone concentration in perfusate before and after liver perfusion with a buffer containing 300 ng/ml of MDMA. Our findings suggest that the activity of CYP2E1 in rats might decrease only after administration of MDMA at a lethal dose. However, further animal and human studies are needed to confirm our assumption.

The Metabolism and Liver Toxicity of N,N-dimethylformamide in the Isolated Perfused Rat Liver

N,N-dimethylformamide (DMF) is metabolized by the microsomal cytochrome p-450 into mainly N-hydroxymethyl- N-methylformamide (HMMF), which further breaks down to N-methyformamide (NMF). However, the detailed mechanism of its toxicity remains unclear. We investigated the metabolism and the toxicity of DMF using the isolated perfused liver model. DMF was added to the recirculating perfusate of the isolated perfused rat liver at concentrations of 0, 10 and 25 mM. Samples were collected from the inferior vena cava at 0, 30, 45, 60, 75, and 90 minutes following addition of the DMF. The metabolites of DMF were analyzed using Gas-chromatography (GC). The changes in the rate of oxygen consumption by the DMF were monitored during perfusion. The enzyme activities (aspartic aminotransferase:AST, alanine aminotransferase:ALT, and lactic dehydrogenase:LDH)) in the perfusate were monitored to see if DMF caused hepatotoxicity. As the perfusion progressed, the DMF concentration in the perfusate decreased, but the level of NMF increased to a maximum of 1.16 mM. The rate of oxygen consumption increased at DMF concentrations of 10 mM and 25 mM. However, when a known inhibitor of cytochrome p-450, SKF 525A (300 micro M), was used to pretreat the perfusate prior to the addition of the DMF, the rate of oxygen consumption was significantly inhibited, indicating the cytochrome p-450 system was responsible for the conversion of DMF to NMF. On addition of the DMF, the activities of the enzymes AST, ALT and LDH were significantly increased a time and dose dependent manner. However, following pretreatment with SKF 525A, their releases were inhibited.

Thiobenzamide S-oxidation in perfused rat liver: Ex vivo determination of hepatic flavin-containing monooxygenase activity

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.

The Metabolism and Liver Toxicity of N, N-dimethylformamide in the Isolated Perfused Liver / 대한산업의학회지

N, N-dimethylformamide (DMF) is a solvent which is widely used in the industrial workplace. It causes the liver damages to the chronically exposed workers and is also well known as the harzadous material to generate occupational malignancies. DMF is mainly metabolized into N-hydroxymethyl-N-methylformamide (HMMF) by the microsomal cytochrome p-450. HMMF breaks down to NMF. However, the detailed mechanism of its toxicity are unknown. In this experiment, the metabolism and the toxicity of DMF was investigated using an isolated perfumed liver model. DMF (0, 10, 25mM) were added into recirculating perfusate of the isolated perfused rat liver. Samples were collected at 0, 30, 45, 60, 75, 90 minutes from inferior vena cava. The gas-chromatography was used to analyze the metabolite of DMF, The changes in the oxygen consumption rate by DMF were monitored during perfusion. The enzyme activity (AST, ALT, LDH) in the perfusate were treasured to find out whether DMF causers hepatotoxicity. As perfusion continued, DMF concentration in the perfusate decreased, and NMF 1.16mM was detected. The oxygen consumption rate increased both at 10mM and 25mM DMF concentration. However, when SKF 525A, a known inhibitor of cytochrome p-450, had been pretreated (300uM before DMF addition, the oxygen consumption rate was significantly inhibited, indicating that cytochrome p-450 system is responsible for the conversion to NMF. With DMF addition, the activity of AST, ALT, and LDH significantly increased time dependently and dose dependently. However, the pretreatment of perfused liver with SKF 525A shoved that the release of AST, ALT and LDH was inhibited. In summary, it is found that DMF is metabolized to NMF in liver, and that cytochrome p-450 mono-oxygenase is suggested to play a role in the biotransformation of NMF. The time course of BMF toxicity in relation to NMF formation is compatible with hypothesis that the hepatotoxicity of DMF is mediated via NMF. Further study combined with in vivo experiment through the toxicological approaches is expected.