Oxidant-induced pHi/Ca2+ changes in rat aortic smooth muscle cells. The role of atrial natriuretic peptide.
The aim of this study was to investigate the effects of oxidative stress on PLD activity, [Ca2+]i and pHi levels and the possible relationship among them. Moreover, since atrial natriuretic peptide (ANP) protects against oxidant-induced injury, we investigated the potential protective role of the hormone in rat aortic smooth muscle (RASM) cells exposed to oxidative stress. Water-soluble 2,2'-Azobis (2-amidinopropane) dihydrochloride (AAPH) was used as free radical generating system, since it generates peroxyl radicals with defined reaction and the half time of peroxyl radicals is longer than other ROS. A significant increase of PLD activity was related to a significant decrease in pHi, while [Ca2+]i levels showed an increase followed by a decrease after cell exposure to AAPH. [Ca2+]i changes and pHi fall induced by AAPH were prevented by cadmium which inhibits a plasma membrane Ca2+ ATPase coupled to Ca2+/H+ exchanger, that operates the efflux of Ca2+ coupled to H+ influx. The involvement of PLD in pHi and [Ca2+]i changes was confirmed by calphostin-c treatment, a potent inhibitor of PLD, which abolished all AAPH-induced effects. Pretreatment of RASM cells with pharmacological concentrations of ANP attenuated the AAPH effects on PLD activity as well as [Ca2+]i and pHi changes, while no effects were observed with physiological ANP concentrations, suggesting a possible role of the hormone as defensive effector against early events of the oxidative stress.
De Vito
P
P
Department of Biology, University of Rome 'Tor Vergata', Rome, Italy.
Di Nardo
P
P
Palmery
M
M
Peluso
I
I
Luly
P
P
Baldini
P M
PM
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D009320:Atrial Natriuretic Factor / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D006863:Hydrogen-Ion Concentration; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology*; D010739:Phospholipase D / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species
D016877:Oxidants; D017382:Reactive Oxygen Species; D009320:Atrial Natriuretic Factor; D010739:Phospholipase D; D002118:Calcium