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Control of ascorbic acid efflux in rat luteal cells: role of intracellular calcium and oxygen radicals

Control of ascorbic acid efflux in rat luteal cells: role of intracellular calcium and oxygen radicals
Control of ascorbic acid efflux in rat luteal cells: role of intracellular calcium and oxygen radicals
In luteal cells, prostaglandin (PG)F2a mobilizes intracellular calcium concentration ([Ca]i), generates reactive oxygen species (ROS), depletes ascorbic acid (AA) levels, inhibits steroidogenesis, and ultimately induces cell death. We investigated the hypothesis that [Ca]i mobilization stimulates ROS, which results in depletion of cellular AA in rat luteal cells. We used a self-referencing AA-selective electrode that noninvasively measures AA flux at the extended boundary layer of single cells and fluorescence microscopy with fura 2 and dichlorofluorescein diacetate (DCF-DA) to measure [Ca]i and ROS, respectively. Menadione, a generator of intracellular superoxide radical (O2-), PGF2a, and calcium ionophore were shown to increase [Ca]i and stimulate intracellular ROS. With calcium ionophore and PGF2a, but not menadione, the generation of ROS was dependent on extracellular calcium influx. In unstimulated cells there was a net efflux of AA of 121.5 +/- 20.3 fmol x cm-1 x s-1 (mean +/- SE, n = 8), but in the absence of extracellular calcium the efflux was significantly reduced (10.3 +/- 4.9 fmol x cm-1 x s-1; n = 5, P < 0.05). PGF2a and menadione stimulated AA efflux, but calcium ionophore had no significant effect. These data suggest two AA regulatory mechanisms: Under basal conditions, AA efflux is calcium dependent and may represent recycling and maintenance of an antioxidant AA gradient at the plasma membrane. Under luteolytic hormone and/or oxidative stress, AA efflux is stimulated that is independent of extracellular calcium influx or generation of ROS. Although site-specific mobilization of calcium pools and ROS cannot be ruled out, the release of AA by PGF2a-stimulated luteal cells may occur through other signaling pathways.
0363-6143
C642-C651
Pepperell, John R.
9a4a43c4-0a13-4af8-af57-827c6c052500
Porterfield, D Marshall
39a3346a-f346-4528-960f-3e8805a9b2d4
Keefe, David L.
a1d0a08b-d76a-4d64-b2dd-4d1a5fc04451
Behrman, Harold R.
c5d85ad4-3f94-499a-894d-fcfe01ceaa45
Smith, Peter J.S.
003de469-9420-4f12-8f0e-8e8d76d28d6c
Pepperell, John R.
9a4a43c4-0a13-4af8-af57-827c6c052500
Porterfield, D Marshall
39a3346a-f346-4528-960f-3e8805a9b2d4
Keefe, David L.
a1d0a08b-d76a-4d64-b2dd-4d1a5fc04451
Behrman, Harold R.
c5d85ad4-3f94-499a-894d-fcfe01ceaa45
Smith, Peter J.S.
003de469-9420-4f12-8f0e-8e8d76d28d6c

Pepperell, John R., Porterfield, D Marshall, Keefe, David L., Behrman, Harold R. and Smith, Peter J.S. (2003) Control of ascorbic acid efflux in rat luteal cells: role of intracellular calcium and oxygen radicals. American Journal of Physiology: Cell Physiology, 285 (3), C642-C651. (doi:10.1152/ajpcell.00587.2002). (PMID:12724141)

Record type: Article

Abstract

In luteal cells, prostaglandin (PG)F2a mobilizes intracellular calcium concentration ([Ca]i), generates reactive oxygen species (ROS), depletes ascorbic acid (AA) levels, inhibits steroidogenesis, and ultimately induces cell death. We investigated the hypothesis that [Ca]i mobilization stimulates ROS, which results in depletion of cellular AA in rat luteal cells. We used a self-referencing AA-selective electrode that noninvasively measures AA flux at the extended boundary layer of single cells and fluorescence microscopy with fura 2 and dichlorofluorescein diacetate (DCF-DA) to measure [Ca]i and ROS, respectively. Menadione, a generator of intracellular superoxide radical (O2-), PGF2a, and calcium ionophore were shown to increase [Ca]i and stimulate intracellular ROS. With calcium ionophore and PGF2a, but not menadione, the generation of ROS was dependent on extracellular calcium influx. In unstimulated cells there was a net efflux of AA of 121.5 +/- 20.3 fmol x cm-1 x s-1 (mean +/- SE, n = 8), but in the absence of extracellular calcium the efflux was significantly reduced (10.3 +/- 4.9 fmol x cm-1 x s-1; n = 5, P < 0.05). PGF2a and menadione stimulated AA efflux, but calcium ionophore had no significant effect. These data suggest two AA regulatory mechanisms: Under basal conditions, AA efflux is calcium dependent and may represent recycling and maintenance of an antioxidant AA gradient at the plasma membrane. Under luteolytic hormone and/or oxidative stress, AA efflux is stimulated that is independent of extracellular calcium influx or generation of ROS. Although site-specific mobilization of calcium pools and ROS cannot be ruled out, the release of AA by PGF2a-stimulated luteal cells may occur through other signaling pathways.

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Published date: September 2003

Identifiers

Local EPrints ID: 188835
URI: http://eprints.soton.ac.uk/id/eprint/188835
ISSN: 0363-6143
PURE UUID: 5cf1a2fc-3103-425f-9bee-0926163ba0fe
ORCID for Peter J.S. Smith: ORCID iD orcid.org/0000-0003-4400-6853

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Date deposited: 17 Jun 2011 13:03
Last modified: 21 Nov 2021 03:04

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Contributors

Author: John R. Pepperell
Author: D Marshall Porterfield
Author: David L. Keefe
Author: Harold R. Behrman

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