Dissertation > Excellent graduate degree dissertation topics show

Metabolic Clearances of Phase I and Phase II Pathways for Fibrates Using Rat and Human Liver Microsomes

Author: ZhouYanMi
Tutor: DaiRenKe
School: University of Science and Technology of China
Course: Biochemistry and Molecular Biology
Keywords: Cytochrome P450 enzymes Glucuronosyltransferase enzyme Metabolize Enzyme kinetics Clearance rate Fibrates Drugs
CLC: R96
Type: Master's thesis
Year: 2010
Downloads: 150
Quote: 0
Read: Download Dissertation

Abstract

Through the regulation of peroxisome proliferator-activated receptor α, fibrates are widely used in the treatment of dyslipidemia. As a class of drugs, the fibrates active form has a carboxyl group, to facilitate the metabolic phase Ⅰ and phase Ⅱ enzymes. However, in the process of in vitro metabolism studies of drugs, the two-phase metabolic contribution is often ignored, so in vitro screening system for the simultaneous detection of phase Ⅰ and phase Ⅱ enzymes of metabolism, to predict in vivo clearance is not very mature still challenging. This research often use several fibrates (gemfibrozil Roach, clofibrate, Fino Bate, this bezafibrate) metabolic stability in rat and human liver microsomes. To start three different reaction system by separately or simultaneously adding metabolic cofactor NADPH and UDPGA cytochrome P450 enzymes and UGT enzyme mediated biotransformation. Substrate elimination method, determination of the apparent enzyme kinetic parameters of these drugs in rat liver microsomes: Michaelis constant Km, the maximum reaction rate Vmax and intrinsic clearance CLint. The Fibrates Gem, a phase oxidation metabolic reaction system apparent Km, Vmax and CLint were 11 ± 4 μM and 1861 ± 967 nmol / min / mg, 172 ± 22μl/min/mg. Km values ??in the Gem glucuronic acid combined with apparent Km values ??of the reaction and a phase reaction considerable (11 ± 1μM). Vmax (6993 ± 1183 nmol / min / mg) in the two-phase system of metabolic reactions and calculated CLint (643 ± 26μl/min/mg) value than one phase reaction about 5 times higher in the system, the instructions in Gem metabolic processes in two-phase pathway is more important than one phase of metabolic pathways. , Km values ??in the one-phase and two-phase joint metabolic reaction system (8 ± 3 μm) is the smallest in the three systems, Vmax values ??(6100 ± 3041 nmol / min / mg), and the two-phase system of metabolic reactions Vmax values about the same, however the CLint value (798 ± 103μl/min/mg) is the largest of the three systems. Another fibrate drugs CPIB obtained by the same method in one phase metabolism, two phase metabolism, one phase and two-phase combined metabolic three reaction system Km value is 0.04 ± 0.004 μm, respectively, 2 ± 1μM, 2 ± 1μM. Vmax values ??in the three reaction system were 2.3 ± 0.3nmol/min/mg, 163 ± 113 nmol / min / mg, 64 ± 49 nmol / min / mg. The CLint value corresponding, respectively, is 43 ± 11μl/min/mg, 88 ± 12μl/min/mg, 119 ± 15μl/min/mg. Other research fibrates intrinsic clearance rate is very low. NADPH and UDPGA start phase reaction and the contribution to the two-phase reaction in gefitinib Roach metabolic clearance process research, we found that the P450-mediated pathway accounted for P450 and UGT joint referral guide means 22%, UGT mediated way to account for 81%. Similarly, clofibrate acid metabolism, P450 and UGT-mediated pathway accounted for 36% and 74% of the P450 and UGT United mediated pathway. These data show that a separate monitoring NADPH or UDPGA dependent pathway may cause a certain deviation, the body can not represent the actual biological conversions, because they are competing pathways. We also found that the clearance rate species differences, but whether in rat liver microsomes or major metabolic pathway in human liver microsomes phase II pathways are fibrates.

Metabolic Clearances of Phase I and Phase II Pathways for Fibrates Using Rat and Human Liver Microsomes

Abstract

Related Dissertations