Abnormal Ca2+ signalling in vascular endothelial cells from spontaneously hypertensive rats: role of free radicals.
OBJECTIVE
To test the hypothesis that the Ca2+ signal transduction process in endothelial cells from genetically hypertensive rats (SHR) is affected by an overproduction of free radicals.


METHODS
The Ca2+ response to the inositol 1,4,5-triphosphate (IP3) mobilizing agonist, ATP, was measured using the fluorescent probe, fura-2, in endothelial cells from Sprague-Dawley rats, and in young and age-matched genetically hypertensive rats (SHR). The effect of free radicals and reducing agents on the intracellular release of Ca2+ and IP3productionwas determined in resting and ATP-stimulated cells. Experiments were also performed to compare the level of expression and enzymatic activity of catalase and superoxide dismutase (SOD) in endothelial cells from SHR and Sprague-Dawley rats.


RESULTS
The exposure of aortic endothelial cells from Sprague-Dawley rats to the free-radical generating system, hypoxanthine + xanthine oxidase (HX/XO), caused a time- and concentration-dependent inhibition of the ATP-induced Ca2+ response. A similar HX/XO-dependent inhibition was also observed in Sprague-Dawley cells stimulated with the endoplasmic reticulum Ca2+-ATPase inhibitor, thapsigargin. Incubation with the antioxidative enzymes, catalase and SOD, had no effect on the ATP-induced Ca2+ release in Sprague-Dawley cells, but led to a strong increase in the internal release of Ca2+ in cells from adult (12 weeks old) or young (3 weeks old) SHR. The effect of antioxidants was not related either to an enhancement of the ATP-induced production of IP3, or to a lower expression and activity of SOD and catalase.


CONCLUSIONS
The present work provides evidence that the Ca2+ signalling process in SHR endothelial cells is affected by an overproduction of free radicals, resulting in a depletion of releasable Ca2+ from IP3-sensitive and insensitive Ca2+ pools. These results point towards a beneficial action of antioxidants on Ca2+ signalling in endothelial cells from models of hypertension.
Pogan
L
L
Département de Physiologie, Faculté de Médecine, Université de Montréal, Québec, Canada.
Garneau
L
L
Bissonnette
P
P
Wu
L
L
Sauvé
R
R
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002374:Catalase / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D005609:Free Radicals / Q000378:metabolism; D006973:Hypertension / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D017207:Rats, Sprague-Dawley / Q000502:physiology; D013482:Superoxide Dismutase / Q000378:metabolism / Q000494:pharmacology
D005609:Free Radicals; D000255:Adenosine Triphosphate; D002374:Catalase; D013482:Superoxide Dismutase