title: Effect of 5-(phenylselenenyl)acyclouridine, an inhibitor of uridine phosphorylase, on plasma concentration of uridine released from 2',3',5'-tri-O-acetyluridine, a prodrug of uridine: relevance to uridine rescue in chemotherapy.
abstract: OBJECTIVE
  The purpose of this investigation was to study the effects of combining oral 5-(phenylselenenyl)acyclouridine (PSAU) with 2',3',5'-tri-O-acetyluridine (TAU) on the levels of plasma uridine in mice. PSAU is a new lipophilic and potent inhibitor of uridine phosphorylase (UrdPase, EC 2.4.2.3), the enzyme responsible for uridine catabolism. PSAU has 100% oral bioavailability and is a powerful enhancer of the bioavailability of oral uridine. TAU is a prodrug of uridine and a far superior source of uridine than uridine itself.
  
  
  METHODS
  Oral TAU was administered to mice alone or with PSAU. The plasma levels of uridine and its catabolites as well as PSAU were measured using HPLC and pharmacokinetic analysis was performed.
  
  
  RESULTS
  Oral administration of 2000 mg/kg TAU increased plasma uridine by over 250-fold with an area under the curve (AUC) of 754 micromol x h/l. Coadministration of PSAU at 30 and 120 mg/kg with TAU further improved the bioavailability of plasma uridine resulting from the administration of TAU alone by 1.7- and 3.9-fold, respectively, and reduced the Cmax and AUC of plasma uracil.
  
  
  CONCLUSIONS
  The exceptional effectiveness of PSAU plus TAU in elevating and sustaining a high plasma uridine concentration could be useful in the management of medical disorders that are remedied by administration of uridine, as well as the rescue or protection from host toxicities of various chemotherapeutic pyrimidine analogues.
authors.affiliation: Department of Pharmacology and Toxicology, Comprehensive Cancer Center, University of Alabama at Birmingham, 35294, USA.
authors.forename: O M
authors.initials: OM
authors.lastname: Ashour
authors.forename: F N
authors.initials: FN
authors.lastname: Naguib
authors.forename: N M
authors.initials: NM
authors.lastname: Goudgaon
authors.forename: R F
authors.initials: RF
authors.lastname: Schinazi
authors.forename: M H
authors.initials: MH
authors.lastname: el Kouni
mesh_terms: D000085:Acetates; D000818:Animals; D001682:Biological Availability; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D005260:Female; D051379:Mice; D016566:Organoselenium Compounds / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D011355:Prodrugs / Q000493:pharmacokinetics / Q000494:pharmacology*; D014498:Uracil / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D014529:Uridine / Q000031:analogs & derivatives / Q000097:blood* / Q000493:pharmacokinetics / Q000494:pharmacology*; D014543:Uridine Phosphorylase / Q000037:antagonists & inhibitors
chemical_list: C408044:5-(phenylselenenyl)acyclouridine; D000085:Acetates; D004791:Enzyme Inhibitors; D016566:Organoselenium Compounds; D011355:Prodrugs; C000609666:uridine triacetate; D014498:Uracil; D014543:Uridine Phosphorylase; D014529:Uridine