title: Spatial Variations in Vitreous Oxygen Consumption.
abstract: We investigated the spatial variation of vitreous oxygen consumption in enucleated porcine eyes. A custom made oxygen source was fabricated that could be localized to either the mid or posterior vitreous cavity and steady state vitreous oxygen tension was measured as a function of distance from the source using a commercially available probe. The reaction rate constant of ascorbate oxidation was estimated ex vivo by measuring the change in oxygen tension over time using vitreous harvested from porcine eyes. Vitreous ascorbate from mid and posterior vitreous was measured spectrophotometrically. When the oxygen source was placed in either the mid-vitreous (N = 6) or the posterior vitreous (N = 6), we measured a statistically significant decrease in vitreous oxygen tension as a function of distance from the oxygen source when compared to control experiments without an oxygen source; (p<0.005 for mid-vitreous and p<0.018 for posterior vitreous at all distances). The mid-vitreous oxygen tension change was significantly different from the posterior vitreous oxygen tension change at 2 and 3mm distances from the respective oxygen source (p<0.001). We also found a statistically significant lower concentration of ascorbate in the mid-vitreous as compared to posterior vitreous (p = 0.02). We determined the reaction rate constant, k = 1.61 M(-1) s(-1) ± 0.708 M(-1) s(-1) (SE), of the oxidation of ascorbate which was modeled following a second order rate equation. Our data demonstrates that vitreous oxygen consumption is higher in the posterior vitreous compared to the mid-vitreous. We also show spatial variations in vitreous ascorbate concentration.
authors.affiliation: Department of Biomedical engineering, University of Southern California, Los Angeles, California, United States of America.
authors.forename: Karthik
authors.initials: K
authors.lastname: Murali
authors.affiliation: Department of Electrical Engineering, California Institute of Technology, Pasadena, California, United States of America.
authors.forename: Dongyang
authors.initials: D
authors.lastname: Kang
authors.affiliation: Department of Ophthalmology, University of Southern California, Los Angeles, California, United States of America.
authors.forename: Hossein
authors.initials: H
authors.lastname: Nazari
authors.affiliation: Department of Electrical Engineering, California Institute of Technology, Pasadena, California, United States of America.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Scianmarello
authors.affiliation: Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California, United States of America.
authors.forename: Enrique
authors.initials: E
authors.lastname: Cadenas
authors.affiliation: Department of Electrical Engineering, California Institute of Technology, Pasadena, California, United States of America.
authors.forename: Yu-Chong
authors.initials: YC
authors.lastname: Tai
authors.affiliation: Department of Ophthalmology, University of Southern California, Los Angeles, California, United States of America.|University of Southern California, Eye Institute, Los Angeles, California, United States of America.|University of Southern California, Institute of Biomedical Therapeutics, Los Angeles, California, United States of America.
authors.forename: Amir
authors.initials: A
authors.lastname: Kashani
authors.affiliation: Department of Biomedical engineering, University of Southern California, Los Angeles, California, United States of America.|University of Southern California, Eye Institute, Los Angeles, California, United States of America.|University of Southern California, Institute of Biomedical Therapeutics, Los Angeles, California, United States of America.
authors.forename: Mark
authors.initials: M
authors.lastname: Humayun
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000032:analysis / Q000378:metabolism; D007700:Kinetics; D010100:Oxygen / Q000032:analysis / Q000378:metabolism*; D010101:Oxygen Consumption; D013552:Swine; D014822:Vitreous Body / Q000378:metabolism*
chemical_list: D001205:Ascorbic Acid; D010100:Oxygen