Effects of NO donors and synthase agonists on endothelial cell uptake of L-Arg and superoxide production.
It is commonly believed that the activity of NO synthase (NOS) solely controls NO production from its substrates, L-Arg and O(2). The Michaelis-Menten constant (K(m)) of NOS for L-Arg is in the micromolar range; cellular levels of L-Arg are much higher. However, evidence strongly suggests that cellular supply of L-Arg may become limiting and lead to reduced NO and increased superoxide anion (O(-)(2)*) formation, promoting cardiovascular dysfunction. Uptake of L-Arg into cells occurs primarily (approximately 85%) through the actions of a Na(+)-independent, carrier-mediated transporter (system y(+)). We have examined the effects of NOS agonists (substance P, bradykinin, and ACh) and NO donors (S-nitroso-N-acetyl-penicillamine and dipropylenetriamine NONOate) on transport of L-Arg into bovine aortic endothelial cells (BAEC). Our results demonstrate that NOS agonists increase y(+) transporter activity. A rapidly acting NO donor initially increases L-Arg uptake; however, after longer exposure, L-Arg uptake is suppressed. Exposure of BAEC without L-Arg to substance P and a Ca(2+) ionophore (A-23187) increased O(-)(2)* formation, which was blocked with concurrent presence of L-Arg or the NOS antagonist N(omega)-nitro-L-arginine methyl ester. We conclude that factors including NO itself control y(+) transport function and the production of NO and O(-)(2)*.
Ogonowski
A A
AA
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, Georgia 30912, USA.
Kaesemeyer
W H
WH
Jin
L
L
Ganapathy
V
V
Leibach
F H
FH
Caldwell
R W
RW
D000818:Animals; D001011:Aorta / Q000166:cytology; D001120:Arginine / Q000493:pharmacokinetics; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D001920:Bradykinin / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006834:Hydrazines / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D019335:Nitroarginine / Q000493:pharmacokinetics*; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D014316:Tritium
D004791:Enzyme Inhibitors; D006834:Hydrazines; D020030:Nitric Oxide Donors; C110881:S-nitro-N-acetylpenicillamine; D014316:Tritium; D013481:Superoxides; D019335:Nitroarginine; D013373:Substance P; D001120:Arginine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D010396:Penicillamine; D001920:Bradykinin; D019331:NG-Nitroarginine Methyl Ester