Intracellular mechanisms involved in D-glucose-mediated amplification of agonist-induced Ca2+ response and EDRF formation in vascular endothelial cells.
Prolonged treatment of vascular endothelial cells with pathologically high D-glucose amplifies autacoid-induced Ca2+ mobilization and thus formation of nitric oxide. This study investigated the Ca2+ source for the change in endothelial CA2+ response on agonist stimulation. Pretreatment with high D-glucose (44 vs. 5 mM) enhanced release of intracellular Ca2+ by bradykinin as a result of a 2.0-fold increased formation of inositol 1,4,5-trisphosphate. High D-glucose also amplified Ca2+ influx (2.0-fold). In high D-glucose preincubated cells, stimulation with bradykinin significantly increased transplasmalemmal 45Ca2+ flux (3.2-fold) and caused a 2.0-fold increase in permeability to Mn2+, a surrogate for endothelial plasma membrane Ca2+ channels. A significant 2.0-fold increase occurred in the maximal slope, suggesting a higher rate of Mn2+ (Ca2+) influx. Ca2+ influx, stimulated by an inositol phosphate-independent depletion of intracellular Ca2+ stores with 2,5-di-(tert-butyl)-hydroquinone was also significantly increased 2.4-fold by high D-glucose, with no effect on intracellular Ca2+ release. D-glucose failed to modulate resting or stimulated cAMP levels. We suggest that prolonged exposure to pathologically high D-glucose increases formation of inositol polyphosphates, thus increasing Ca2+ release. Ca2+ entry is increased by amplification of unknown signal transduction mechanisms triggered by Ca2+ store depletion.
Department of Internal Medicine, University of Graz, Austria.
T C
TC
Wascher
H
H
Toplak
G J
GJ
Krejs
S
S
Simecek
W R
WR
Kukovetz
W F
WF
Graier
D000818:Animals; D001011:Aorta; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D004533:Egtazic Acid / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D008345:Manganese / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D011189:Potassium Chloride / Q000494:pharmacology; D013552:Swine
D002132:Calcium Radioisotopes; D009569:Nitric Oxide; D008345:Manganese; D004533:Egtazic Acid; D011189:Potassium Chloride; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D005947:Glucose; D001920:Bradykinin; D002118:Calcium