caa a22 4500 475819160 CHVBK 20180406123817.0 cr unu---uuuuu 170329e20001201xx s 000 0 eng 10.1007/s002280000227 doi (NATIONALLICENCE)springer-10.1007/s002280000227 Mycophenolic acid glucuronidation and its inhibition by non-steroidal anti-inflammatory drugs in human liver and kidney [Elektronische Daten] [M. Vietri, A. Pietrabissa, F. Mosca, G.M. Pacifici] Abstract.: Objective: The aims of this investigation were to study the glucuronidation of mycophenolic acid (MPA) in human liver and kidney and to search for a compound that inhibits MPA glucuronidation among the non-steroidal anti-inflammatory drugs (NSAIDs). Methods: A sensitive and reproducible radiometric assay was developed to measure the rate of MPA glucuronidation in human liver and kidney microsomes. The assay employed uridine 5′-diphosphate-[U-14C]-glucuronic acid (UDPGA) and MPA-glucuronide was isolated by TLC. The final concentrations of UDPGA and MPA necessary were 1mM (liver), and MPA concentration was 0.5mM (kidney). The inhibition of MPA glucuronidation was studied with 18 NSAIDs and tacrolimus. Results: Glucuronosyl transferase activity followed Michaelis-Menten kinetics and the K m (mean±SD; mM) was 0.31±0.06 (liver; n=5) and 0.28±0.07 (kidney; n=5; P=0.555); the Vmax (mean±SD; nmol/mg per minute) was 5.2±1.4 (liver; n=5) and 10.5±1.2 (kidney; n=5; P=0.0005). The MPA glucuronidation rates (mean±SD; nmol/min/mg) were 3.3±0.9 (liver; n=10) and 7.8±1.5 (kidney; n=10; P=0.0002). The rate of MPA glucuronidation ranged between 2.0 and 5.1nmol/mg per minute with a 2.5-fold variation (liver) and between 5.7 and 9.8nmol/mg per minute with a 1.7-fold variation (kidney). The inhibition study was performed in liver and revealed that the percentage of control ranged from 8%±3% (niflumic acid) to 119%±16% (Ketoralac). The inhibition curves for MPA glucuronidation rate were determined with the four most effective inhibitors: niflumic acid, flufenamic acid, mefenamic acid and diflunisal. Their IC50 estimates (µM) were 8±1, 19±9, 63±8 and 109±15, respectively (liver), and 8±2, 13±2, 49±4 and 122±18, respectively (kidney). The IC50 estimate for niflumic acid was eightfold lower than the peak plasma levels after a single oral dose of 250mg of this drug. Conclusion: The human liver and kidney are important sites of MPA glucuronidation. MPA glucuronidation was inhibited to various extents by different NSAIDs and the four most effective inhibitors were niflumic acid, flufenamic acid, mefenamic acid and diflunisal. These drugs have similar molecular structures consisting of two aromatic rings bearing a carboxylic group. Springer-Verlag, 2000 Mycophenolic acid Mycophenolate mofetil Glucuronosyl transferase Liver Kidney nationallicence Vietri M. Department of Neurosciences, Section of Pharmacology, Medical School, Via Roma 55, 56126 Pisa, Italy aut Pietrabissa A. Department of Oncology, Section of Surgery, Cisanello Hospital at University of Pisa, 56124 Cisanello, Italy aut Mosca F. Department of Oncology, Section of Surgery, Cisanello Hospital at University of Pisa, 56124 Cisanello, Italy aut Pacifici G.M. Department of Neurosciences, Section of Pharmacology, Medical School, Via Roma 55, 56126 Pisa, Italy aut European Journal of Clinical Pharmacology Springer-Verlag 56/9-10(2000-12-01), 659-664 0031-6970 56:9-10<659 2000 56 228 https://doi.org/10.1007/s002280000227 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s002280000227 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Vietri M. Department of Neurosciences, Section of Pharmacology, Medical School, Via Roma 55, 56126 Pisa, Italy aut NATIONALLICENCE 700 1- Pietrabissa A. Department of Oncology, Section of Surgery, Cisanello Hospital at University of Pisa, 56124 Cisanello, Italy aut NATIONALLICENCE 700 1- Mosca F. Department of Oncology, Section of Surgery, Cisanello Hospital at University of Pisa, 56124 Cisanello, Italy aut NATIONALLICENCE 700 1- Pacifici G.M. Department of Neurosciences, Section of Pharmacology, Medical School, Via Roma 55, 56126 Pisa, Italy aut NATIONALLICENCE 773 0- European Journal of Clinical Pharmacology Springer-Verlag 56/9-10(2000-12-01), 659-664 0031-6970 56:9-10<659 2000 56 228 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer