Modulation of angiotensin II effect by adhesion to the extracellular matrix in hypertensive rat

This study was to assess the role of different components of the extracellu lar matrix (ECM) on the mobilization of Ca-i(++) induced by angiotensin II in vascular smooth muscle cells (VSMC) from hypertensive (SHR) and normoten sive (WKY) rats. The effect of AII (10-6 M) on Ca-i(++) release was studied in VSMC isolated from the aorta of 5-week-old WKY and SHR using fluorescent imaging microsc opy (fura-2). Ca-i(++) mobilization was characterized by amplitude, slope o f Ca-i(++) increase and total amount of Ca-i(++). Cells were cultured on gl ass coverslips (control) or coated with either collagen I, collagen IV, vit ronectin, fibronectin and extracellular matrix (ECM) and studied at conflue nce between passage 3 and 9. A significant increase of Ca-i(++) released by AII has been observed with c ells from WKY cultured on collagen I (meam+/-SEM, amplitude: 192+/-12% of c ontrol values, slope: 194+/-13%, total amount Ca-i(++): 173+/-12%, n=270, p less than or equal to 0.0001 for each, unpaired t-test). Conversely, respo nse with SHR was not significatively modified. Ca-i(++) mobilization was no t significatively modified after culture of VSMC from SHR and WKY on collag en IV A significative decrease of the slope (WKY: 66+/-6%, p less than or e qual to 0.0001; SHR: 83+/-5%, p less than or equal to 0.03) and of the amou nt of Ca-i(++) (WKY: 74+/-7%, p less than or equal to 0.01: SHR: 74+/-5%, p less than or equal to 0.01) has been observed after culture of VSMC from t he 2 strains on vitronectin. A decrease in amplitude (53+/-3%, p less than or equal to 0.0001), slope (38+/-4%, p less than or equal to 0.0001) and Ca -i(++) release (69+/-5%, p less than or equal to 0.004, n=106) has been obs erved in VSMC from SHR seeded on fibronectin. Conversely, in VSMC from WKY, Ca-i(++) mobilisation has not been modified compared with control cells. C ulture of VSMC from SHR on ECM induced a significative decrease of amplitud e (49+/-2%), slope (54+/-4%) and Ca-i(++) release (53+/-3%, p less than or equal to 0.0001 for each, n=122), while in WKY, ECM induced a significative stimulation of these parameters (amplitude: 157+/-11%, slope: 149+/-13% an d Ca-i(++) release: 130+/-9%, p less than or equal to 0.0001 for each, n=24 7). These results show that the Ca-i(++) mobilization induced by AII is modifie d by the adhesion of cells to different ECM components. This suggests a mod ulation of the A II-associated signalling events via the focal adhesion poi nts. Furthermore, a difference in this modulation is observed between SHR a nd WKY when cells are seeded on collagen I, fibronectin or ECM. These modul ations of Ca-i(++) mobilization could play a role in the regulation of grow th and differentiation of cells during the developement of hypertension.