title: Vitreal pharmacokinetics of biotinylated ganciclovir: role of sodium-dependent multivitamin transporter expressed on retina.
abstract: OBJECTIVE
  The objective of this study was to investigate the role of sodium-dependent multiple vitamin transporter (SMVT) on Biotin-Ganciclovir (biotin-GCV) uptake on both human retinal pigmented epithelium cell line (ARPE-19) and rabbit retina. Study also aims to delineate the vitreal pharmacokinetics of biotin-GCV.
  
  
  METHODS
  ARPE-19 was employed to study the in vitro uptake experiments. New Zealand white albino rabbits were used to study in vivo retinal uptake and vitreal pharmacokinetics following intravitreal administration of biotin-GCV. In vitro uptake kinetics of [3H] biotin was determined at various initial concentrations. Competitive inhibition studies were conducted in the presence of unlabelled biotin, desthiobiotin, pantothenic acid, and lipoic acid. Various other uptake studies were performed to functionally characterize the transporter. To provide the molecular evidence of this transporter, Reverse Transcription-Polymerase Chain Reaction (RT-PCR) studies were also conducted. In vivo retinal/choroidal uptake studies were carried out with New Zealand albino rabbits. Unconscious animal ocular microdialysis studies were performed in order to evaluate intravitreal pharmacokinetics of GCV and Biotin-GCV.
  
  
  RESULTS
  Uptake of [3H] biotin into ARPE-19 was linear over 7 min, and found to be saturable with K(m) of 138.25 muM and Vmax of 38.85 pmol/min/mg protein. Both pantothenic acid and lipoic acid decreased significantly in uptake of biotin in the concentration-dependent manner. Uptake of biotin into ARPE-19 was found to be temperature, energy, and Na+ dependent but Cl(-)independent. Further, RT-PCR studies identified a band exhibiting presence of hSMVT on ARPE-19. Biotin-GCV is recognized by SMVT system present on the ARPE-19 and rabbit retina. Vitreal Pharmacokinetics profile reveals that most of the parameters were not significantly different for GCV and Biotin-GCV. However, use of Biotin-GCV may result in sustain levels of regenerated GCV in vitreous.
  
  
  CONCLUSIONS
  SMVT was identified and functionally characterized on ARPE-19 cells. Further, Biotin-GCV shares this transport system. Vitreal pharmacokinetics of the conjugate was determined in unconscious rabbit model.
authors.affiliation: Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, Kansas City, Missouri 64110-2499, USA.
authors.forename: Kumar G
authors.initials: KG
authors.lastname: Janoria
authors.forename: Sai H S
authors.initials: SH
authors.lastname: Boddu
authors.forename: Zhiying
authors.initials: Z
authors.lastname: Wang
authors.forename: Durga K
authors.initials: DK
authors.lastname: Paturi
authors.forename: Swapan
authors.initials: S
authors.lastname: Samanta
authors.forename: Dhananjay
authors.initials: D
authors.lastname: Pal
authors.forename: Ashim K
authors.initials: AK
authors.lastname: Mitra
mesh_terms: D000818:Animals; D019540:Area Under Curve; D001710:Biotin / Q000493:pharmacokinetics*; D019921:Biotinylation; D002460:Cell Line; D002829:Choroid / Q000378:metabolism; D016503:Drug Delivery Systems; D015774:Ganciclovir / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D011355:Prodrugs / Q000493:pharmacokinetics*; D011817:Rabbits; D012160:Retina / Q000378:metabolism*; D055213:Retinal Pigment Epithelium / Q000378:metabolism; D027981:Symporters / Q000096:biosynthesis / Q000502:physiology*; D014018:Tissue Distribution; D014822:Vitreous Body / Q000378:metabolism*
chemical_list: D011355:Prodrugs; D027981:Symporters; C119981:biotin transporter; D001710:Biotin; D015774:Ganciclovir