Transcellular transfer of folate across the retinal pigment epithelium

Christy C. Bridges, Amira El-Sherbeny, M. Shamsul Ola, Vadivel Ganapathy, Sylvia B Smith

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

The differential polarized distribution of the folate receptor a (FRα) in the basal membrane and reduced-folate transporter (RFT-1) in the apical membrane was demonstrated previously in the retinal pigment epithelium (RPE). Based on this, we hypothesized that folate would enter the RPE via FRα and exit the cell via RFT-1. To test this, we performed in vitro transport assays using ARPE-19 cells cultured on permeable supports. The cells were grown for 4 weeks and electron microscopic analysis indicated that the cells have the phenotypic features of normal RPE cells including apical microvillous processes and junctional complexes. Measurement of transepithelial resistance showed that the resistance increases in the cells as they differentiate over several weeks. Transport assays showed that ARPE-19 cells transport folate in a basal-to-apical direction, but do not transport this vitamin significantly in the apical-to basal-direction. This was not a diffusional process, as the paracellular markers inulin and sucrose were transferred across the cell monolayer at a much lower level. The presence of FRα in the basal membrane was demonstrable by folate binding and that of RFT-1 in the apical membrane by blockade of folate transport by RFT-1-specific antibody. This study represents the first in vitro demonstration of transcellular transfer of folate across RPE and suggests that folate is transported from the choriocapillaris to the adjacent photoreceptor cells in vivo by the concerted action of FRα in the basal membrane and RFT-1 in the apical membrane.

Original languageEnglish (US)
Pages (from-to)129-138
Number of pages10
JournalCurrent Eye Research
Volume24
Issue number2
DOIs
StatePublished - Jan 1 2002

Fingerprint

Retinal Pigment Epithelium
Folic Acid
Membranes
Reduced Folate Carrier Protein
Photoreceptor Cells
Inulin
Vitamins
Sucrose
Cultured Cells
Electrons

Keywords

  • Folate receptor alpha
  • Folate transport
  • Polarization
  • Reduced-folate transporter
  • Retinal pigment epithelium

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

Cite this

Transcellular transfer of folate across the retinal pigment epithelium. / Bridges, Christy C.; El-Sherbeny, Amira; Ola, M. Shamsul; Ganapathy, Vadivel; Smith, Sylvia B.

In: Current Eye Research, Vol. 24, No. 2, 01.01.2002, p. 129-138.

Research output: Contribution to journalArticle

Bridges, Christy C. ; El-Sherbeny, Amira ; Ola, M. Shamsul ; Ganapathy, Vadivel ; Smith, Sylvia B. / Transcellular transfer of folate across the retinal pigment epithelium. In: Current Eye Research. 2002 ; Vol. 24, No. 2. pp. 129-138.
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