title: Molecular identification and cellular localisation of GSH synthesis, uptake, efflux and degradation pathways in the rat ciliary body.
abstract: The aim of this study is to determine the contribution of the ciliary epithelium to glutathione (GSH) levels in the aqueous by mapping GSH metabolism and transport pathways in the rat ciliary body. Using a combination of molecular and immunohistochemical techniques, we screened and localised enzymes and transporters involved in GSH synthesis, uptake, efflux and degradation. Our findings indicate that both the pigmented epithelial (PE) and the non-pigmented epithelial (NPE) cell layers are capable of accumulating precursor amino acids for GSH synthesis, but only the NPE cells appear to be involved in the direct uptake of precursor amino acids from the stroma. The localisation of GSH efflux transporters to the PE cell and PE-NPE interface indicates that GSH and potentially GSH-S conjugates can be removed from the ciliary epithelium into the stroma, while the location of GSH efflux transporters to the basolateral membrane of the NPE indicates that these cells can mediate GSH secretion into the aqueous. GSH secreted by the ciliary into the aqueous would remain largely intact due to the absence of the GSH degradation enzymes γ-glutamyltranspeptidase (γ-GGT) labelling at the basolateral membrane of the NPE. Therefore, it appears that the ciliary epithelium contains the molecular machinery to mediate GSH secretion into the aqueous.
authors.affiliation: Department of Optometry and Vision Science, NZ National Eye Centre, University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Ankita
authors.initials: A
authors.lastname: Umapathy
authors.forename: Loi Uyen
authors.initials: LU
authors.lastname: Tran
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Donaldson
authors.forename: Julie C
authors.initials: JC
authors.lastname: Lim
mesh_terms: D000818:Animals; D001692:Biological Transport; D002924:Ciliary Body / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism*; D005978:Glutathione / Q000096:biosynthesis / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D029362:Organic Anion Transporters, Sodium-Independent; D018384:Oxidative Stress; D051381:Rats; D005723:gamma-Glutamyltransferase
chemical_list: D026901:Membrane Transport Proteins; D029362:Organic Anion Transporters, Sodium-Independent; C086860:glutathione transporter; C114338:organic anion transport protein 3; D005723:gamma-Glutamyltransferase; D005978:Glutathione