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


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. AJP Cell Physiology, 285, (3), C642-C651. (10.​1152/​ajpcell.​00587.​2002). (PMID:12724141).

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Description/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.

Item Type: Article
ISSNs: 0363-6143 (print)
1522-1563 (electronic)
Subjects: Q Science > QH Natural history > QH301 Biology
Q Science > QP Physiology
Divisions: University Structure - Pre August 2011 > Other
ePrint ID: 188835
Date Deposited: 17 Jun 2011 13:03
Last Modified: 27 Mar 2014 19:42
URI: http://eprints.soton.ac.uk/id/eprint/188835

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