The insulin-induced increase of guanosine-3',5'-cyclic monophosphate in human platelets is mediated by nitric oxide.
To investigate whether the insulin-induced increase of guanosine-3',5'-cyclic monophosphate (cGMP) in human platelets is mediated by nitric oxide or is influenced by the nitric oxide precursor L-arginine, we measured cGMP in platelet-rich plasma obtained from healthy volunteers incubated for 3 min with human recombinant insulin (0, 240, 480, 960, and 1,920 pmol/l) both with and without 1) a 20-min incubation with the nitric oxide-synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) (50, 70, 100, and 1,000 micromol/l; n = 5 for each dose) and 2) a 20-min incubation with the nitric oxide precursor L-arginine (300 micromol/l; n = 6). In a first set of experiments, insulin induced a dose-dependent cGMP increase, from 9.8 +/- 0.8 to 45.6 +/- 5.5 pmol/10(9) platelets (P = 0.0001); in the presence of 1 mmol/l L-NMMA, this increase was blunted, cGMP being 8.9 +/- 1.4 and 11.1 +/- 2.2 pmol/10(9) platelets at 0 and 1,920 pmol/l insulin, respectively (NS). In the experiments with 70 and 100 micromol/l L-NMMA, the insulin effect on cGMP was inhibited, whereas 50 micromol/l L-NMMA did not blunt this insulin effect. In another set of experiments carried out to investigate the effects of L-arginine, insulin induced a dose-dependent cGMP increase, from 23.6 +/- 6.9 to 59.0 +/- 12.0 pmol/10(9) platelets (P = 0.0001); with L-arginine, basal cGMP values increased to 35.5 +/- 6.6 pmol/10(9) platelets (P = 0.05), and insulin maintained its ability to enhance dose-dependently cGMP values, which rose to 76.8 +/- 19.4 pmol/10(9) platelets (P = 0.003). This study carried out in human platelets demonstrates that the cGMP increase induced by insulin, which accounts for the antiaggregating effect of the hormone, is mediated by nitric oxide.
Trovati
M
M
Department of Clinical and Biological Sciences of the University of Turin, San Luigi Gonzaga Hospital, Orbassano, Italy.
Massucco
P
P
Mattiello
L
L
Piretto
V
V
Cavalot
F
F
Mularoni
E
E
Anfossi
G
G
D000328:Adult; D000704:Analysis of Variance; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D006152:Cyclic GMP / Q000097:blood*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000097:blood; D011994:Recombinant Proteins / Q000494:pharmacology; D019323:omega-N-Methylarginine
D004791:Enzyme Inhibitors; D007328:Insulin; D011994:Recombinant Proteins; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP