Agonist-regulated L-arginine uptake in human platelets. Evidence against intracellular utilization of the amino acid.
L-arginine uptake takes place in human platelets through a saturable high affinity Na(+)-independent process mediated by the y(+) carrier for cationic amino acids. In the present study the effect of thrombin and collagen on L-arginine transport in human platelets was investigated. Thrombin significantly affected L-arginine uptake whereas collagen was uneffective. In particular, thrombin increased Vmax of the uptake by 77%, while it reduced the affinity of the carrier for L-arginine. The effect of thrombin on the transport process did not result in any increase in L-arginine metabolism since no conversion of the amino acid, either to L-citrulline (indicative of the presence of the L-arginine/nitric oxide pathway) or to any other metabolite, could be detected in resting or stimulated platelets.
Vasta
V
V
Department of Biochemical Sciences, University of Firenze, Italy.
Meacci
E
E
Maurenzig
L
L
Farnararo
M
M
Bruni
P
P
D001120:Arginine / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D001792:Blood Platelets / Q000378:metabolism*; D003094:Collagen / Q000494:pharmacology*; D006801:Humans; D013917:Thrombin / Q000494:pharmacology*
D003094:Collagen; D001120:Arginine; D013917:Thrombin