title: Function and regulation of taurine transport at the inner blood-retinal barrier.
abstract: In the retina, taurine exerts a number of neuroprotective functions as an osmolyte and antioxidant. The purpose of the present study was to elucidate the taurine transport system(s) at the inner blood-retinal barrier (BRB). [(3)H]Taurine transport at the inner BRB was characterized using in vivo integration plot analysis and a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells). The expression of the taurine transporter (TauT) was demonstrated by RT-PCR and immunoblot analyses. The apparent influx permeability clearance of [(3)H]taurine in the rat retina was found to be 259 muL/(ming retina), supporting carrier-mediated influx transport of taurine at the BRB. [(3)H]Taurine uptake by TR-iBRB2 cells was Na(+)-, Cl(-)- and concentration-dependent with a K(m) of 22.2 muM and inhibited by TauT inhibitors, such as beta-alanine and hypotaurine. RT-PCR and immunoblot analyses demonstrated that TauT is expressed in TR-iBRB2 and primary cultured human retinal endothelial cells. The uptake of [(3)H]taurine and the expression of TauT mRNA in TR-iBRB2 cells increased under hypertonic conditions but decreased following pretreatment with excess taurine. In conclusion, TauT most likely mediates taurine transport and regulate taurine transport at the inner BRB.
authors.affiliation: Department of Pharmaceutics, Graduate School of Medical and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Tomi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Terayama
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Isobe
authors.forename: Fuminobu
authors.initials: F
authors.lastname: Egami
authors.forename: Akihisa
authors.initials: A
authors.lastname: Morito
authors.forename: Michio
authors.initials: M
authors.lastname: Kurachi
authors.forename: Sumio
authors.initials: S
authors.lastname: Ohtsuki
authors.forename: Young-Sook
authors.initials: YS
authors.lastname: Kang
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Terasaki
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Hosoya
mesh_terms: D000818:Animals; D001483:Base Sequence; D001693:Biological Transport, Active; D001813:Blood-Retinal Barrier / Q000502:physiology*; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D042783:Endothelial Cells / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013654:Taurine / Q000378:metabolism*; D000099247:Taurine Transporters
chemical_list: D017931:DNA Primers; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D013654:Taurine; D000099247:Taurine Transporters