Characterization of the L-arginine:nitric oxide pathway in human platelets.
1. The activation of the L-arginine: nitric oxide (NO) pathway during aggregation of human platelets by adenosine 5'-diphosphate (ADP), arachidonic acid, thrombin and the calcium ionophore A23187 and its inhibition by NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester (L-NAME) and N-iminoethyl-L-ornithine (L-NIO) were studied. The inhibition of the cytosolic platelet NO synthase by these compounds was also examined. 2. Platelet aggregation induced by ADP (1-10 microM) and arachidonic acid (0.1-10 microM), but not that induced by thrombin (1-30 mu ml-1) or A23187 (1-10 nM), was inhibited by L-, but not D-arginine (1-30 microM). However, in the presence of a subthreshold concentration of prostacyclin (0.1 nM) or of M & B 22948 (1 microM), a selective inhibitor of guanosine 3':5'-cyclic monophosphate (cyclic GMP) phosphodiesterase, L-arginine caused concentration-dependent inhibition of aggregation induced by all of these aggregating agents. 3. L-NMMA, L-NAME and L-NIO (all at 1-30 microM), but not their D-enantiomers, enhanced to the same extent platelet aggregation induced by ADP, arachidonic acid and thrombin without affecting that induced by A23187. 4. In the presence of 300 microM L-arginine, the NO synthase in platelet cytosol was inhibited by L-NMMA, L-NAME and L-NIO with IC50s of 74 +/- 9, 79 +/- 8 and 8.5 +/- 1.5 microM (n = 3), respectively. 5. These results indicate that the L-arginine: NO pathway in human platelets plays a role in the modulation of platelet aggregation.
Wellcome Research Laboratories, Beckenham, Kent.
M W
MW
Radomski
R M
RM
Palmer
S
S
Moncada
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors / Q000097:blood; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D001120:Arginine / Q000031:analogs & derivatives / Q000097:blood* / Q000494:pharmacology; D001792:Blood Platelets / Q000201:enzymology / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000097:blood*; D019001:Nitric Oxide Synthase; D009952:Ornithine / Q000031:analogs & derivatives / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D013237:Stereoisomerism; D013917:Thrombin / Q000494:pharmacology; D019323:omega-N-Methylarginine
D001095:Arachidonic Acids; D010975:Platelet Aggregation Inhibitors; D019323:omega-N-Methylarginine; D016718:Arachidonic Acid; D009569:Nitric Oxide; C065027:N(G)-iminoethylornithine; D000001:Calcimycin; D000244:Adenosine Diphosphate; D001120:Arginine; D009952:Ornithine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D013917:Thrombin; D019331:NG-Nitroarginine Methyl Ester