Breast cancer resistance protein (Bcrp1/Abcg2) limits net intestinal uptake of quercetin in rats by facilitating apical efflux of glucuronides.

The intestinal absorption of the flavonoid quercetin in rats is limited by the secretion of glucuronidated metabolites back into the gut lumen. The objective of this study was to determine the role of the intestinal efflux transporters breast cancer resistance protein (Bcrp1)/Abcg2 and multidrug resistance-associated protein 2 (Mrp2)/Abcc2. To study the possible involvement of Mrp2, we compared intestinal uptake of quercetin-3-glucoside between control and Mrp2-deficient rats, using an in situ intestinal perfusion system. The contribution of Bcrp1 was determined using the specific inhibitor fumitremorgin C (FTC) in Mrp2-deficient rats. Furthermore, vectorial transport of quercetin was studied in Madin-Darby canine kidney (MDCK)II cells transfected with either human MRP2 or murine Bcrp1. In these MDCKII cells, we showed an efficient efflux-directed transport of quercetin by mouse Bcrp1, whereas in control and MRP2-transfected cells no vectorial transport of quercetin was observed. In Mrp2-deficient rats, intestinal uptake of quercetin from quercetin-3-glucoside, efflux of quercetin glucuronides to the gut lumen, and plasma concentration of quercetin were similar to that in control rats. When intestinal Bcrp1 was inhibited by FTC in Mrp2-deficient rats, total plasma concentrations of quercetin and its methylated metabolite isorhamnetin after 30 min of perfusion were more than twice that of controls (12.3 +/- 1.5 versus 5.6 +/- 1.3 muM; p < 0.01), whereas uptake of free quercetin from the intestinal lumen was not affected. Instead, inhibition of Bcrp1 lowered the efflux of quercetin glucuronides into the perfusion fluid by approximately 4-fold. In conclusion, Bcrp1 limits net intestinal absorption of quercetin by pumping quercetin glucuronides back into the lumen

Evaluation Report

Drug-induced liver injury (DILI) is a common reason for drug withdrawal from the market. An important cause of DILI is drug-induced cholestasis. One of the major players involved in drug-induced cholestasis is the bile salt efflux pump (BSEP; ABCB11). Inhibition of BSEP by drugs potentially leads to cholestasis due to increased (toxic) intrahepatic concentrations of bile acids with subsequent cell injury. In order to investigate the possibilities for in silico prediction of cholestatic effects of drugs, we developed a mechanistic biokinetic model for human liver bile acid handling populated with human in vitro data. For this purpose we considered nine groups of bile acids in the human bile acid pool, i.e. chenodeoxycholic acid, deoxycholic acid, the remaining unconjugated bile acids and the glycine and taurine conjugates of each of the three groups. Michaelis-Menten kinetics of the human uptake transporter Na+-taurocholate cotransporting polypeptide (NTCP; SLC10A1) and BSEP were measured using NTCP-transduced HEK293 cells and membrane vesicles from BSEP-overexpressing HEK293 cells. For in vitro-in vivo scaling, transporter abundance was determined by LC-MS/MS in these HEK293 cells and vesicles as well as in human liver tissue. Other relevant human kinetic parameters were collected from literature, such as portal bile acid levels and composition, bile acid synthesis and amidation rate. Additional empirical scaling was applied by increasing the excretion rate with a factor 2.4 to reach near physiological steady-state intracellular bile acid concentrations (80 μM) after exposure to portal vein bile acid levels. Simulations showed that intracellular bile acid concentrations increase 1.7 fold in the presence of the BSEP inhibitors and cholestatic drugs cyclosporin A or glibenclamide, at intrahepatic concentrations of 6.6 and 20 μM, respectively. This simplified model provides a tool for a first indication whether drugs at therapeutic concentrations might cause cholestasis by inhibiting BSEP. © 2018 The Author

A precisão experimental para diferentes manejos na cultura do milho Experimental precision for different corn production managements

Foram estudados os efeitos de formas de controle de plantas daninhas, uniformidade de distribuição das sementes e adubo, e proteção das plantas jovens aos insetos sobre o erro experimental. As formas de manejo foram organizadas em três experimentos no delineamento inteiramente casualizado, sendo cada repetição das formas de manejo composta por seis linhas de 5,0m de uma cultivar precoce de milho. O controle de plantas daninhas, realizado pelo método químico ou pela capina manual não proporcionou diferença significativa no erro experimental. A estimativa do erro experimental da forma de distribuição de adubo mais uniforme foi menor do que na forma desuniforme. A distribuição de sementes na linha de semeadura, realizada manualmente, e não eqüidistante acarreta um menor erro experimental para rendimento de grãos e população final de plantas, se comparada com a distribuição eqüidistante.<br>The effects of weed control procedures, fertilizer and seed distribution uniformity, and young plant protection to insects over the experimental error were studied. The management procedures were organized in three experiments using a completely randomized design. Each replication of the management procedure was made by 6 lines of 5m using a short-day com cultivar. The weed control, made by herbicides or manual control did not present significam difference in the experimental error. The evaluation of the experimental error of the more uniform fertilizer distribution was smaller than the desuniform distribution. The line seed distribution, done by hand and not with the same distance, caused a smaller experimental error for grain yield and final population than the line seed distribution with the same distance