STIMULATION OF 2 VASCULAR SMOOTH MUSCLE-DERIVED CELL-LINES BY ANGIOTENSIN-II - DIFFERENTIAL 2ND MESSENGER RESPONSES LEADING TO MITOGENESIS

1 We show here that angiotensin II (AII) and endothelin-1 (ET-1) stimu late [H-3]-thymidine incorporation in a smooth muscle cell line derive d from aortae of spontaneously hypertensive rats (SHR), but not in cel ls derived from normotensive controls (WKY). We have used the differen tial response of the two cell lines to investigate the relationship be tween second messenger systems and the mitogenic response. 2 AII produ ced an increase in accumulation of inositol 1,4,5-triphosphate which w as greater in the SHR-derived cell line than in the WKY cells. 3 All g ave an increase in cytosolic Ca2+ in each of the cell lines, with both a larger peak (15-30 s) and plateau response (2 min) 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+. 4 Phospholipase D activity was studied by monitoring the formation of [P-3]-phosphatidyl butanol in (32)Pi prelabelled cells. AII stimulation gave a larger pho spholipase D response in SHR-derived cells, while ET-1 gave a larger r esponse in WKY-derived cells. 5 Stimulation of SHR-derived cells with 100 nM AII for 1 h, followed by 19 h in the absence of agonist, stimul ated [H-3]-thymidine incorporation over the next 4 h. When the 1 h sti mulation with All was in the presence of increasing concentrations of butanol, which diverts the product of the phospholipase D pathway, the re was a loss of stimulated [H-3]-thymidine incorporation which was si gnificant at 10 mM butanol and at 30-50 mM reached a maximum loss of 4 0%. 6 Contrasting with this there was no apparent loss of ET-1-stimula ted thymidine incorporation when butanol was present at concentrations up to 40 mM. 7 These results suggest that phospholipase D is one of s everal pathways in the mitogenic response of SHR-derived vascular smoo th muscle cells to AII.