The aim of this study was to optimize methods for quantifying 13 uridine 59-diphosphate-glucuronosyltransferase (UGT) isoforms (UGT1A1, 1A3, 1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B10, 2B15, and 2B17) in human liver, intestinal, and kidney microsomes, and in recombinant human UGT-expressing insect cell membranes (rhUGTs) by targeted peptide-based quantification using liquid chromatography-tandem mass spectrometry. Production of targeted peptides was compared by combining three denaturing agents (urea, sodium deoxycholate, and octyl glucoside) and three denaturing temperatures (37°C, 60°C, and 95°C) followed by tryptic digestion for 2-20 hours. Denaturing conditions and digestion times yielding high production efficiency varied markedly among isoforms and specimens, indicating the importance of specific optimization. Each UGT isoform was quantified using the methods found to be optimal.

Brain capillary endothelial cell lines (TR-BBB) were established from a recently developed transgenic rat harboring temperature-sensitive simian virus 40 (ts SV 40) large T-antigen gene (Tg rat) and used to characterize the endothelial marker, transport activity, and mRNA expression of transporters and tight-junction strand proteins at the blood-brain barrier (BBB). These cell lines expressed active large T-antigen and grew well at 33 degrees C with a doubling-time of about 22-31 hr, but did not grow at 39 degrees C. TR-BBBs expressed the typical endothelial marker, von Willebrand factor, and exhibited acetylated low-density lipoprotein uptake activity. Although the gamma-glutamyltranspeptidase activity in TR-BBBs was approximately 13% of that of the brain capillary fraction of a normal rat, it was localized in the apical side, suggesting that it reflects the functional polarity of the in vivo BBB. The mRNA of tight-junction strand proteins such as claudine-5, occludin, and junctional adhesion molecule are expressed in TR-BBB13. Drug efflux transporter, P-glycoprotein, with a molecular weight of 170 kDa was expressed in all TR-BBBs and mdr 1a, mdr 1b, and mdr 2 mRNA were detected in TR-BBBs using RT-PCR. Moreover, mrp1 mRNA was expressed in all TR-BBBs. Influx transporter, GLUT-1, expressed at 55 kDa was revealed by Western blot analysis. It had 3-O-methyl-D-glucose (3-OMG) uptake activity which was concentration-dependent with a Michaelis-Menten constant of 9.86 +/- 1.20 mM. The mRNA of large neutral amino acid transporter, which consists of LAT-1 and 4F2hc was expressed in TR-BBBs. In conclusion, the conditionally immortalized rat brain capillary endothelial cell lines (TR-BBB) had endothelial makers, expressed mRNA for tight-junction strand proteins and the influx and efflux transporters and produced GLUT-1, which is capable of 3-OMG transport activity.

Five immortalized brain capillary endothelial cell lines (TM-BBB1-5) were established from 3 transgenic mice harboring temperaturesensitive simian virus 40 large T-antigen gene (Tg mouse). These cell lines expressed active large Tantigen and grew well at 33°C with a doubling time of about 20 to 30 hours. TM-BBBs also grew at 37°C but not at 39°C. However, growth was restored when the temperature of the culture was lowered to 33°C. Although significant amounts of large T-antigen were shown to be present in the cell culture at 33°C, there was less of this complex at 37°C and 39°C. TMBBBs expressed the typical endothelial marker, von Willebrand factor, and exhibited acetylated lowdensity lipoprotein uptake activity. The alkaline phosphatase and Ȗ-glutamyltranspeptidase activity in

Aspartic acid (Asp) undergoes L-isomer-selective efflux transport across the blood-brain barrier (BBB). This transport system appears to play an important role in regulating L-and D-Asp levels in the brain. The purpose of this study was to identify the responsible transporters and elucidate the mechanism for L-isomer-selective Asp transport at the BBB. The L-isomer-selective uptake of Asp by conditionally immortalized mouse brain capillary endothelial cells used as an in vitro model of the BBB took place in an Na + -and pH-dependent manner. This process was inhibited by system ASC substrates such as L-alanine and L-serine, suggesting that system ASC transporters, ASCT1 and ASCT2, are involved in the L-isomer selective transport. Indeed, L-Asp uptake by oocytes injected with either ASCT1 or ASCT2 cRNA took place in a similar manner to that in cultured BBB cells, whereas no significant D-Asp uptake occurred. Although both ASCT1 and ASCT2 mRNA were expressed in the cultured BBB cells, the expression of ASCT2 mRNA was 6.7-fold greater than that of ASCT1. Moreover, immunohistochemical analysis suggests that ASCT2 is localized at the abluminal side of the mouse BBB. These results suggest that ASCT2 plays a key role in L-isomer-selective Asp efflux transport at the BBB. Keywords: amino acid transporter, ASCT, aspartic acid, blood-brain barrier, brain capillary endothelial cells, isomerselective.