Residues Met89 and Ser160 in the Human Equilibrative Nucleoside Transporter 1 (hENT1) Affect hENT1's Affinity for Adenosine, Guanosine, NBMPR and

Abstract The human equilibrative nucleoside transporter 1 (hENT1) is an important modulator of the physiological action of adenosine. We identified amino acid residues involved in adenosine transport using a yeast-based assay to rapidly screen and identify randomly generated hENT1 mutants that exhibited decreased sensitivity to inhibition of adenosine transport by various hENT1 competitive inhibitors. We identified Met89 and alone. Collectively, these data indicate that TMD2 (Met89) and TMD4 (Ser160) of hENT1 interact and are important in conferring sensitivity to NBMPR. In contrast, Ser160 and Met89 of hENT1 respectively play a dominant role in conferring sensitivity to dipyridamole and adenosine/guanosine affinity

Prediction of Gestational Age-Dependent Induction of In Vivo Hepatic CYP3A Activity Based on HepaRG Cells and Human Hepatocytes Running Title: Prediction of Gestational Age-Dependent Induction of In Vivo Hepatic CYP3A Activity

ABSTRACT In pregnant women, CYP3A activity increases by 100% during the third trimester (T3). Due to logistical and ethical constraints, little is known about the magnitude of CYP3A induction during the first (T1) and second (T2) trimesters. Our laboratory has shown that sandwich-cultured human hepatocytes (SCHH) and HepaRG cells have the potential to predict the magnitude of in vivo induction of CYP3A activity likely to be observed in T1 and T2. Therefore, we incubated SCHH and HepaRG cells with plasma concentrations of various pregnancy-related hormones (PRHs, individually or in combination) observed during T1, T2, or T3 in pregnant women. Then, Based on these data, we conclude that C remains the major inducer of CYP3A activity earlier in gestation. Moreover, we predict that the magnitude of CYP3A induction during T1 and T2 will be similar to that observed during T3 (~100% increase vs. postpartum). This prediction is consistent with the observation of similar increase in T2 and T3 oral clearance of indinavir (a CYP3A cleared drug) vs. postpartum

Increased glyburide clearance in the pregnant mouse model. Drug Metab Dispos 38:1403–1406. Address correspondence to:

c) Number of text pages: 22 Abstract Glyburide (GLB) is an oral sulfonylurea, commonly used for the treatment of gestational diabetes mellitus. It has been reported that the clearance of GLB in pregnant women is significantly higher than that in non-pregnant women. The molecular mechanism by which pregnancy increases the clearance of GLB is not known, but may be caused by increased CYP3A activity. As liver tissue from pregnant women is not readily available, in the present study, we investigated the mechanism of such pregnancy-related changes in GLB disposition in a mouse model. We demonstrated that the systemic clearance of GLB in pregnant mice was increased approximately 2-fold (p < 0.01) as compared with non-pregnant mice, a magnitude of change similar to that observed in the clinical study. Plasma protein binding of GLB in mice was not altered by pregnancy. The half-life of GLB depletion in hepatic S-9 fractions of pregnant mice was significantly shorter than that of non-pregnant mice. Moreover, GLB depletion was markedly inhibited by ketoconazole, a potent inhibitor of mouse Cyp3a, suggesting that GLB metabolism in mice is primarily mediated by hepatic Cyp3a. These data suggest that the increased systemic clearance of GLB in pregnant mice is likely caused by an increase in hepatic Cyp3a activity during pregnancy, and provide a basis for further mechanistic understanding and analysis of pregnancy-induced alterations in the disposition of GLB and drugs that are predominantly and extensively metabolized by CYP3A/Cyp3a. DMD #33837