Stimulation of two vascular smooth muscle‐derived cell lines by angiotensin II: differential second messenger responses leading to mitogenesis

Abstract

We show here that angiotensin II (All) and endothelin‐l (ET‐1) stimulate [3H]‐thymidine incorporation in a smooth muscle cell line derived from aortae of spontaneously hypertensive rats (SHR), but not in cells derived from normotensive controls (WKY). We have used the differential response of the two cell lines to investigate the relationship between second messenger systems and the mitogenic response. All produced an increase in accumulation of inositol 1,4,5‐triphosphate which was greater in the SHR‐derived cell line than in the WKY cells. All gave an increase in cytosolic Ca2+ in each of the cell lines, with both a larger peak (15–30 s) and plateau response (2min) in the SHR cells. ET‐1 gave an enhanced response in the SHR‐derived cells with respect to the peak but not the plateau of cytosolic Ca2+. Phospholipase D activity was studied by monitoring the formation of [3P]‐phosphatidylbutanol in 32Pi prelabelled cells. All stimulation gave a larger phospholipase D response in SHR‐derived cells, while ET‐1 gave a larger response in WKY‐derived cells. Stimulation of SHR‐derived cells with 100 nM All for 1 h, followed by 19 h in the absence of agonist, stimulated [3H]‐thymidine incorporation over the next 4 h. When the 1 h stimulation with All was in the presence of increasing concentrations of butanol, which diverts the product of the phospholipase D pathway, there was a loss of stimulated [3H]‐thymidine incorporation which was significant at 10 mM butanol and at 30‐50mM reached a maximum loss of 40%. Contrasting with this there was no apparent loss of ET‐1‐stimulated thymidine incorporation when butanol was present at concentrations up to 40 mM. 7 These results suggest that phospholipase D is one of several pathways in the mitogenic response of SHR‐derived vascular smooth muscle cells to All. 1995 British Pharmacological Society