Glucuronidation of iodothyronines in rat liver is catalyzed by at least three UDP-glucuronyltransferases (UGTs): bilirubin UGT, phenol UGT, and androsterone UGT. Bilirubin and phenol UGT activities are regulated by thyroid hormone, but the effect of thyroid status on hepatic glucuronidation of iodothyronines is unknown. We examined the effects of hypothyroidism induced by treatment of rats with...

We investigated whether the effects of intestinal glucuronidation on the first-pass effect can be predicted from in vitro data for UDP-glucuronosyltransferase (UGT) substrates. Human in vitro intrinsic glucuronidation clearance (CL(int, UGT)) for 11 UGT substrates was evaluated using pooled intestinal microsomes (4.00-4620 μl · min⁻¹ · mg⁻¹) and corrected by the free fraction in the microsomal ...

Five cloned human hepatic UDP-glucuronosyltransferase (UGT) cDNAs were stably expressed in tissue culture cell lines. More than 100 drugs and xenobiotics were used as substrates for glucuronidation catalyzed by the cloned human transferases to determine the chemical structures accepted as substrates. UGT-HP1 exhibited a limited substrate specificity for planar phenolic compounds, whereas UGT-HP...

Mycophenolic acid (MPA), the active metabolite of the immunosuppressant mycophenolate mofetil is primarily metabolized by glucuronidation. The nature of UDP-glucuronosyltransferases (UGTs) involved in this pathway is still debated. The present study aimed at identifying unambiguously the UGT isoforms involved in the production of MPA-phenyl-glucuronide (MPAG) and MPA-acylglucuronide (AcMPAG). A...

UDP-glucuronosyltransferase (UGT) is highly expressed in the small intestine and catalyzes the glucuronidation of small molecules, which may affect the oral bioavailability of drugs. However, no method of predicting the in vivo observed fraction of absorbed drug (F(a)F(g)) affected by UGT has yet been established. Here, we investigated the relationship between F(a)F(g) and in vitro clearance of...

The measurement of the effect of new chemical entities on human UDP-glucuronosyltransferase (UGT) marker activities using in vitro experimentation represents an important experimental approach in drug development to guide clinical drug-interaction study designs or support claims that no in vivo interaction will occur. Selective high-performance liquid chromatography-tandem mass spectrometry fun...

Previous studies have shown the importance of the addition of albumin for characterization of hepatic glucuronidation in vitro; however, no reports exist on the effects of albumin on renal or intestinal microsomal glucuronidation assays. This study characterized glucuronidation clearance (CL(int, UGT)) in human kidney, liver, and intestinal microsomes in the presence and absence of bovine serum...

Many laboratories use recombinant UDP-glucuronosyltransferases (UGTs), expressed in baculovirus-infected insect cells, for drug glucuronidation studies. We have infected Sf9 insect cells with increasing amounts of recombinant baculovirus, encoding either UGT1A9 or UGT2B7, and measured both glucuronidation activity and immunodetectable UGT in the resulting cell homogenates. The correlation betwe...

UDP-galactose reaches the Golgi lumen through the UDP-galactose transporter (UGT) and is used for the galactosylation of proteins and lipids. Ceramides and diglycerides are galactosylated within the endoplasmic reticulum by the UDP-galactose:ceramide galactosyltransferase. It is not known how UDP-galactose is transported from the cytosol into the endoplasmic reticulum. We transfected ceramide g...

UDP-Glucuronosyltransferases (UGTs) are phase II biotransformation enzymes that glucuronidate numerous endobiotic and xenobiotic substrates. Glucuronidation increases the water solubility of the substrate and facilitates renal and biliary excretion of the resulting glucuronide conjugate. UGTs have been divided into two gene families, UGT1 and UGT2. Tissue distribution of UGTs has not been thoro...