Fig. 7.

PA stimulates mammalian target of rapamycin (mTOR)/S6K1/S6 pathway independent of phosphatidylinositol 3-kinase (PI3-kinase) activation. A: inhibition of PI3-kinase failed to significantly block S6K1 phosphorylation induced by PA. Quiescent SMCs were pretreated with 10 μmol/l LY-294002 and 100 nmol/l rapamycin for 30 min and incubated with 100 μmol/l PA for 10 min. The phosphorylation of S6K1 (⁴²¹Thr/⁴²⁴Ser) and total S6K1 was detected by Western blot analysis. B: inhibition of PI3-kinase does not reduce 5-HT-induced PLD activation. After cells were prelabeling with [³H]myristic acid for 18 h, SMCs were treated with LY-294002 (10 μmol/l) for 30 min and then stimulated with 5-HT for 20 min. The accumulation of [³H]PBt was measured as noted in materials and methods for the cellular lipid extract from each group. The bar graphs for blots in A and B represent means ± SD for n = 3. *Significant difference from untreated cells (P < 0.05). **Significant difference from 5-HT-treated cells (P < 0.05) in A.