Lens transport of ascorbic acid in guinea pigs, normal, galactose-fed and with congenital cataract

B. V. Zlokovic, J. B. Mackic, J. S. Zigler, N. Kaplowitz, R. Kannan

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Abstract

Purpose. To determine transport of circulating ascorbic acid (AA) by the lens epithelium in guinea pigs, normal, galactose-fed and with hereditary cataract. Methods. Hartley guinea pigs, 4 weeks old (either sex), and age matched galactose-fed (50% galactose and 0.5 g/kg AA) and 13/N strain guinea pigs with congenital cataract, were administered [14C]-AA (2 μM) by an in situ eye perfusion technique. The radioactivity in the epithelium and cortex was determined by scintillation spectrometry and radio-HPLC. Levels of AA, reduced and oxidized glutathione, GSH and GSSG, were determined by HPLC. Results. Transport of [14C]-AA into the aqueous and epithelium of normal animals occurred against > 600-fold and 6-fold aqueous/plasma and epithelium/aqueous concentration gradients. The concentration of [14C]-AA in the epithelium significantly exceeded aqueous concentration after 1 min. Preliminary studies demonstrated Na+-dependent AA transport in epithelial mRNA injected X. laevis oocytes. After 3 days of galactose feeding, there was a 50% increase in epithelial AA transport, 71% and 35% decrease in GSH transport and levels, 3.4-fold increase in GSSG/GSH epithelial ratio and 52% increase in malondialdehyde suggesting oxidant stress. In 13/N strain (heterozygous), transport of [14C]-AA was enhanced by > 2-fold, while GSH levels and transport were reduced by ∼ 70%. Conclusions. Specific lens AA transport is enhanced in galactose and congenital cataract in guinea pigs possibly providing an alternative antioxidant for the lens in the presence of reduced GSH levels and transport.

Original languageEnglish (US)
Pages (from-to)S881
JournalInvestigative Ophthalmology and Visual Science
Volume37
Issue number3
StatePublished - Feb 15 1996

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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