Measurement of NO production in endothelial cells during incubation with hydroxyurea in presence or not of inhibitors of PKA and PKB/Akt. (A) After preincubation period with 20 μM H-89 (PKA inhibitor), 50 μM LY294002, and 0.1 μM wortmannin (PI 3-kinase inhibitors), HUVECs were treated with 2 different concentrations of hydroxyurea (20 and 50 μM), and aliquots were collected for measurement after 1 hour of incubation. (B) TrHBMECs were preincubated with PKA and PI 3-kinase inhibitors, and measurements were made after 1 hour of incubation with hydroxyurea. Values are mean ± SEM (n = 3). ^*P < .05 and ^**P < .01 compared with cells treated with only hydroxyurea.