S-nitrosoglutathione/glutathione disulphide/Cu2+-dependent stimulation of L-arginine transport in human platelets.
In this study, we have examined the effects of authentic nitric oxide (NO), NO+ (NOBF4), glutathione (GSH), glutathione disulphide (GSSG), and S-nitrosoglutathione (GSNO) in the presence and absence of Cu2+, which thermally releases NO from S-nitrosothiols on the transport of L-arginine into the human platelet. The K(M,apparent) was unaffected by NO, NO+, GSH, and GSNO. However, Cu2+ lowered K(M,apparent) by approximately 2.85-fold. Cu2+-dependent lowering of K(M,apparent) was also observed, albeit to a smaller extent when this ion was mixed with GSH (approximately 1.9-fold lower) and GSNO (approximately 2.0-fold). GSSG also lowered K(M,apparent) by approximately 1.5-fold. The Vmax,apparent of L-arginine uptake was unaffected by NO, NO+, GSH, and Cu2+. Vmax,apparent was stimulated by to the largest extent by GSNO (approximately 2.28-fold) and GSNO plus Cu2+ (approximately 2.7-fold). GSSG and GSH plus Cu2+ also increased Vmax,apparent by approximately 1.9-fold. When these parameters are expressed in terms of transport efficiency (Vmax/K(M)) the largest effect of nearly 4.7-fold (over controls) was obtained by a combination of GSNO plus Cu2+. These results suggest that platelet L-Arg transport is not affected either by NO or NO+ but by a thiol-disulphide exchange reactions on the platelet L-Arg transporter, brought about by GSNO and GSSG. Based on these results, a GSNO/GSSG/Cu2+ dependent regulatory mechanism for the uptake of L-arginine in human platelets has been proposed.
Howard
C M
CM
Department of Chemistry and Biochemistry, University of Windsor, Ontario, Canada.
Sexton
D J
DJ
Mutus
B
B
D001120:Arginine / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D001792:Blood Platelets / Q000378:metabolism*; D003300:Copper / Q000378:metabolism; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology; D019803:Glutathione Disulfide / Q000494:pharmacology*; D006801:Humans; D009569:Nitric Oxide / Q000494:pharmacology*; D009603:Nitroso Compounds / Q000494:pharmacology*; D015539:Platelet Activation; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D026422:S-Nitrosoglutathione
D009603:Nitroso Compounds; D010975:Platelet Aggregation Inhibitors; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; D003300:Copper; D001120:Arginine; D005978:Glutathione; D019803:Glutathione Disulfide