Phosphatidylinositol 3-kinase (PI3-K) has been shown to mediate insulin and
insulin-like growth factor-1 (IGF-1)-induced nitric oxide (NO) generation
and, thus, vascular tone. A role for P13-K in G-protein-coupled receptor si
gnal transduction has been reported. As beta (beta (2))-adrenergic vascular
actions are partly dependent on NO, we have investigated the role of P13-K
in isoproterenol. (Iso) and IGF-1 induced endothelial NO synthase (ecNOS)
activity in rat aortic endothelial cells (RAEC). Cell lysates of RAEC, expo
sed to Iso (10 mu mol/L) for 5 min and 6 h, and to IGF-1 (100 nM) for 10 mi
n and 6 h, or pretreated with P13-K inhibitor Wortmannin (WT17), were used
for measuring P13-K activity, p85kDa regulatory protein, and citrulline pro
duction. Results show that Iso and IGF-1 increased a p85 subunit and citrul
line production, and also enhanced P-32 incorporation into PIP,. Pretreatme
nt with WT inhibited Iso-stimulated ecNOS, as well as, P13-K activity. Iso
enhanced association of ecNOS with the triton X-100-insoluble fraction of R
AEC. These data indicate that the endothelial cell P13-K pathway mediates,
in part, the release of NO and subsequent vasorelaxation in response to thi
s beta -agonist, as well as, IGF-1. (C) 2001 Academic Press.