Vitamin C transport in oxidized form across the rat blood-retinal barrier

Ken Ichi Hosoya, Akito Minamizono, Kazunori Katayama, Tetsuya Terasaki, Masatoshi Tomi

Research output: Contribution to journalArticle

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Abstract

PURPOSE. To elucidate the mechanisms of vitamin C transport across the blood-retinal barrier (BRB) in vivo and in vitro. METHODS. [14C] Dehydroascorbic acid (DHA) and [14C]ascorbic acid (AA) transport in the retina across the BRB were examined using in vivo integration plot analysis in rats, and the transport mechanism was characterized using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) as an in vitro model of the inner BRB. RESULTS. The apparent influx permeability clearance (Kin) per gram of retina of [14C]DHA and [ 14C]AA was found to be 2.44 × 103 μL/(min · g retina) and 65.4 μL/(min · g retina), respectively. In the retina and brain, the Kin of [14C]DHA was approximately 38 times greater than that of [14C]AA. whereas there was no major difference in the heart. The Kin of [14C]DHA in the retina was eight times greater than that in the brain. HPLC analysis revealed that most of the vitamin C accumulated in AA form in the retina. These results suggest that vitamin C is mainly transported in DHA form across the BRB and accumulates in AA form in the rat retina. In an in vitro uptake study in TR-iBRB2 cells, the initial uptake rate of [14C]DHA was 37 times greater than that of [14C]AA, which is in agreement with the results of the in vivo study. [14C]DHA uptake by TR-iBRB2 cells took place in an Na +-independent and concentration-dependent manner with a Km of 93.4 μM. This process was inhibited by substrates and inhibitors of glucose transporters. [14C]DHA uptake was inhibited by D-glucose in a concentration-dependent manner with a 50% inhibition concentration of 5.56 mM. Quantitative real-time PCR and immunostaining analyses revealed that expression of GLUT1 and -3 was greater than that of the Na+-dependent L-ascorbic acid transporter (SVCT)-2 in TR-iBRB2 cells. CONCLUSIONS. Vitamin C is mainly transported across the BRB as DHA mediated through facilitative glucose transporters and accumulates as AA in the rat retina.

Original languageEnglish
Pages (from-to)1232-1239
Number of pages8
JournalInvestigative Ophthalmology and Visual Science
Volume45
Issue number4
DOIs
Publication statusPublished - 2004 Apr
Externally publishedYes

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Blood-Retinal Barrier
Dehydroascorbic Acid
Ascorbic Acid
Retina
Facilitative Glucose Transport Proteins
Sodium-Coupled Vitamin C Transporters
Brain

ASJC Scopus subject areas

  • Ophthalmology

Cite this

Vitamin C transport in oxidized form across the rat blood-retinal barrier. / Hosoya, Ken Ichi; Minamizono, Akito; Katayama, Kazunori; Terasaki, Tetsuya; Tomi, Masatoshi.

In: Investigative Ophthalmology and Visual Science, Vol. 45, No. 4, 04.2004, p. 1232-1239.

Research output: Contribution to journalArticle

Hosoya, Ken Ichi ; Minamizono, Akito ; Katayama, Kazunori ; Terasaki, Tetsuya ; Tomi, Masatoshi. / Vitamin C transport in oxidized form across the rat blood-retinal barrier. In: Investigative Ophthalmology and Visual Science. 2004 ; Vol. 45, No. 4. pp. 1232-1239.
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abstract = "PURPOSE. To elucidate the mechanisms of vitamin C transport across the blood-retinal barrier (BRB) in vivo and in vitro. METHODS. [14C] Dehydroascorbic acid (DHA) and [14C]ascorbic acid (AA) transport in the retina across the BRB were examined using in vivo integration plot analysis in rats, and the transport mechanism was characterized using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) as an in vitro model of the inner BRB. RESULTS. The apparent influx permeability clearance (Kin) per gram of retina of [14C]DHA and [ 14C]AA was found to be 2.44 × 103 μL/(min · g retina) and 65.4 μL/(min · g retina), respectively. In the retina and brain, the Kin of [14C]DHA was approximately 38 times greater than that of [14C]AA. whereas there was no major difference in the heart. The Kin of [14C]DHA in the retina was eight times greater than that in the brain. HPLC analysis revealed that most of the vitamin C accumulated in AA form in the retina. These results suggest that vitamin C is mainly transported in DHA form across the BRB and accumulates in AA form in the rat retina. In an in vitro uptake study in TR-iBRB2 cells, the initial uptake rate of [14C]DHA was 37 times greater than that of [14C]AA, which is in agreement with the results of the in vivo study. [14C]DHA uptake by TR-iBRB2 cells took place in an Na +-independent and concentration-dependent manner with a Km of 93.4 μM. This process was inhibited by substrates and inhibitors of glucose transporters. [14C]DHA uptake was inhibited by D-glucose in a concentration-dependent manner with a 50{\%} inhibition concentration of 5.56 mM. Quantitative real-time PCR and immunostaining analyses revealed that expression of GLUT1 and -3 was greater than that of the Na+-dependent L-ascorbic acid transporter (SVCT)-2 in TR-iBRB2 cells. CONCLUSIONS. Vitamin C is mainly transported across the BRB as DHA mediated through facilitative glucose transporters and accumulates as AA in the rat retina.",
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T1 - Vitamin C transport in oxidized form across the rat blood-retinal barrier

AU - Hosoya, Ken Ichi

AU - Minamizono, Akito

AU - Katayama, Kazunori

AU - Terasaki, Tetsuya

AU - Tomi, Masatoshi

PY - 2004/4

Y1 - 2004/4

N2 - PURPOSE. To elucidate the mechanisms of vitamin C transport across the blood-retinal barrier (BRB) in vivo and in vitro. METHODS. [14C] Dehydroascorbic acid (DHA) and [14C]ascorbic acid (AA) transport in the retina across the BRB were examined using in vivo integration plot analysis in rats, and the transport mechanism was characterized using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) as an in vitro model of the inner BRB. RESULTS. The apparent influx permeability clearance (Kin) per gram of retina of [14C]DHA and [ 14C]AA was found to be 2.44 × 103 μL/(min · g retina) and 65.4 μL/(min · g retina), respectively. In the retina and brain, the Kin of [14C]DHA was approximately 38 times greater than that of [14C]AA. whereas there was no major difference in the heart. The Kin of [14C]DHA in the retina was eight times greater than that in the brain. HPLC analysis revealed that most of the vitamin C accumulated in AA form in the retina. These results suggest that vitamin C is mainly transported in DHA form across the BRB and accumulates in AA form in the rat retina. In an in vitro uptake study in TR-iBRB2 cells, the initial uptake rate of [14C]DHA was 37 times greater than that of [14C]AA, which is in agreement with the results of the in vivo study. [14C]DHA uptake by TR-iBRB2 cells took place in an Na +-independent and concentration-dependent manner with a Km of 93.4 μM. This process was inhibited by substrates and inhibitors of glucose transporters. [14C]DHA uptake was inhibited by D-glucose in a concentration-dependent manner with a 50% inhibition concentration of 5.56 mM. Quantitative real-time PCR and immunostaining analyses revealed that expression of GLUT1 and -3 was greater than that of the Na+-dependent L-ascorbic acid transporter (SVCT)-2 in TR-iBRB2 cells. CONCLUSIONS. Vitamin C is mainly transported across the BRB as DHA mediated through facilitative glucose transporters and accumulates as AA in the rat retina.

AB - PURPOSE. To elucidate the mechanisms of vitamin C transport across the blood-retinal barrier (BRB) in vivo and in vitro. METHODS. [14C] Dehydroascorbic acid (DHA) and [14C]ascorbic acid (AA) transport in the retina across the BRB were examined using in vivo integration plot analysis in rats, and the transport mechanism was characterized using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) as an in vitro model of the inner BRB. RESULTS. The apparent influx permeability clearance (Kin) per gram of retina of [14C]DHA and [ 14C]AA was found to be 2.44 × 103 μL/(min · g retina) and 65.4 μL/(min · g retina), respectively. In the retina and brain, the Kin of [14C]DHA was approximately 38 times greater than that of [14C]AA. whereas there was no major difference in the heart. The Kin of [14C]DHA in the retina was eight times greater than that in the brain. HPLC analysis revealed that most of the vitamin C accumulated in AA form in the retina. These results suggest that vitamin C is mainly transported in DHA form across the BRB and accumulates in AA form in the rat retina. In an in vitro uptake study in TR-iBRB2 cells, the initial uptake rate of [14C]DHA was 37 times greater than that of [14C]AA, which is in agreement with the results of the in vivo study. [14C]DHA uptake by TR-iBRB2 cells took place in an Na +-independent and concentration-dependent manner with a Km of 93.4 μM. This process was inhibited by substrates and inhibitors of glucose transporters. [14C]DHA uptake was inhibited by D-glucose in a concentration-dependent manner with a 50% inhibition concentration of 5.56 mM. Quantitative real-time PCR and immunostaining analyses revealed that expression of GLUT1 and -3 was greater than that of the Na+-dependent L-ascorbic acid transporter (SVCT)-2 in TR-iBRB2 cells. CONCLUSIONS. Vitamin C is mainly transported across the BRB as DHA mediated through facilitative glucose transporters and accumulates as AA in the rat retina.

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