Ca2+-mediated ascorbate release from coronary artery endothelial cells.
1.--The addition of Ca(2+) ionophore A23187 or ATP to freshly isolated or cultured pig coronary artery endothelial cells (PCEC) potentiated the release of ascorbate (Asc). Cultured PCEC were used to characterize the Ca(2+)-mediated release. An increase in Ca(2+)-mediated Asc release was observed from PCEC preincubated with Asc, Asc-2-phosphate or dehydroascorbic acid (DHAA). 2.--The effects of various ATP analogs and inhibition by suramin were consistent with the ATP-induced release being mediated by P2Y2-like receptors. 3.--ATP-stimulated Asc release was Ca(2+)-mediated because (a) ATP analogs that increased Asc release also elevated cytosolic [Ca(2+)], (b) Ca(2+) ionophore A23187 and cyclopiazonic acid stimulated the Asc release, (c) removing extracellular Ca(2+) and chelating intracellular Ca(2+)inhibited the ATP-induced release, and (d) inositol-selective phospholipase C inhibitor U73122 also inhibited this release. 4.--Accumulation of Asc by PCEC was examined at Asc concentrations of 10 microM (Na(+)-Asc symporter not saturated) and 5 mM (Na(+)-Asc symporter saturated). At 10 microM Asc, A23187 and ATP caused an inhibition of Asc accumulation but at 5 mM Asc, both the agents caused a stimulation. Substituting gluconate for chloride did not affect the basal Asc uptake but it abolished the effects of A23187. 5.--PCEC but not pig coronary artery smooth muscle cells show a Ca(2+)- mediated Asc release pathway that may be activated by agents such as ATP.
Davis
Kim A
KA
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
Samson
Sue E
SE
Best
Kelly
K
Mallhi
Kanwaldeep K
KK
Szewczyk
Magdalena
M
Wilson
John X
JX
Kwan
Chiu-Yin
CY
Grover
Ashok K
AK
D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013552:Swine
D000975:Antioxidants; D007476:Ionophores; D000001:Calcimycin; D000255:Adenosine Triphosphate; D001205:Ascorbic Acid; D002118:Calcium