Angiotensin II type 1 receptor-mediated increase in cytosolic Ca 2+ and proliferation in mesothelial cells

Abstract

We investigated the Ca 2+ signaling pathways of the response to angiotensin II in pleural mesothelial cells and the role of these Ca 2+ signaling pathways in mesothelial cell proliferation. Rat pleural mesothelial cells were maintained in vitro, and the Ca 2+ movement to angiotensin II was evaluated using the fluorescent Ca 2+ indicator fura 2. Furthermore, proliferation of mesothelial cells was assessed using a spectrophotometric 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyl-2 H-tetrasodium bromide (MTT) assay. Angiotensin II (1 pM–100 μM) induced in mesothelial cells a biphasic elevation of intracellular Ca 2+ concentration ([Ca 2+] i) that consisted of a transient initial component, followed by a sustained component. Neither removal of extracellular Ca 2+ nor inhibition of Ca 2+ influx by 1 μM nifedipine affected the angiotensin II-induced initial transient elevation of [Ca 2+] i in mesothelial cells. Nifedipine did not block angiotensin II-induced sustained elevation of [Ca 2+] i. Angiotensin II (1 pM–100 μM) had a proliferative effect on mesothelial cells in a dose-dependent manner. Angiotensin II type 1 (AT 1) receptor antagonist ([Sar 1, Ile 8]angiotensin II) inhibited both angiotensin II-induced elevation of [Ca 2+] i and proliferation of mesothelial cells. Pertussis toxin did not affect angiotensin II-induced responses. These results suggest that angiotensin II-induced responses to mesothelial cells are extremely dependent on the angiotensin AT 1 receptor coupled with pertussis toxin-insensitive G protein.