ObjectiveThis study investigates the growth effects and associated signaling pathways of angiotensin II (Ang II) in human vascular smooth muscle cells.MethodsCultured vascular smooth muscle cells derived from resistance arteries (< 300 μm diameter) from subcutaneous gluteal biopsies of healthy subjects (n= 6) and human aortic vascular smooth muscle cells were used. Cells were studied between passages 3 and 6. Both3H-thymidine and3H-leucine incorporation were measured as indices of vascular smooth muscle cell hyperplasia (DNA synthesis) and cell hypertrophy (protein synthesis), respectively. Growth effects of Ang II (10−12= 10−6mol/l), in the absence and presence of 10−5mol/l losartan (AT1antagonist) and PD123319 (AT2antagonist), were determined. Ang II-induced effects were compared to those of endothelin-1. To determine whether extracellular signal-regulated kinase (ERK)-dependent pathways play a role in Ang II-mediated growth, cells were pretreated with the selective ERK kinase (MEK) inhibitor, PD98059 (10−5mol/l). ERK activation was determined by Western blot in the absence and presence of PD98059.ResultsAng II dose-dependently increased3H-thymidine incorporation in cells from aorta (Emax= 276 ± 10.4% of control) and resistance arteries (Emax= 284 ± 5.1% of control). Ang II also stimulated3H-leucine incorporation in cells from aorta (Emax= 162 ± 11.6 of control) and resistance arteries (Emax175 ± 10% of control). Unlike Ang II, endothelin-1 failed to significantly alter cellular growth, except at high concentrations (> 10−7mol/l), where it had a weak stimulatory effect. Losartan, but not PD123319, blocked Ang II-stimulated growth responses. Ang II significantly increased phosphorylation of ERK-1 and ERK-2, with maximum responses obtained at 5 min. PD98059 inhibited Ang II-stimulated ERK activity and abrogated agonist-induced DNA and protein synthesis. Losartan, but not PD123319 inhibited Ang II-induced phosphorylation of ERK-1 and ERK-2.ConclusionsAng II stimulates both hyperplasia and hypertrophy in vascular smooth muscle cells from human arteries. These growth effects are mediated via Ang II receptors of the AT1subtype that are linked to ERK-dependent signaling pathways.