Bradykinin and angiotensin II-induced [Ca2+]i rise in cultured rat pituitary folliculo-stellate cells

Folliculo-stellate cells of the anterior pituitary are thought to modulate pituitary hormone secretion through a paracrine mechanism. Angiotensin I! and pituitary adenylate cyclase-activating polypeptide (PACAP) have previously been shown to increase the intracellular Ca2+ concentration ([Ca2+](i)) of these cells. In the present study, we examined the effects of various peptides such as bradykinin, angiotensin II, endothelin-1, PACAP, galanin and neurotensin by Ca2+-imaging of folliculo-stellate cells in primary culture. Bradykinin and angiotensin II increased [Ca2+](i) in folliculo-stellate cells. Both responses were completely suppressed by thapsigargin and were significantly suppressed by the phospholipase C inhibitor, U-73122. Ryanodine did not significantly modify the responses. A B-2 antagonist and angiotensin II receptor antagonist inhibited the response induced by bradykinin and angiotensin II, respectively. Endothelin-1 and PACAP increased [Ca2+](i) in fewer than 50% of folliculo-stellate cells but galanin and neurotensin did not influence [Ca2+](i) in any of the folliculo-stellate cells tested. These results indicate that bradykinin and angiotensin II increase [Ca2+](i) in folliculo-stellate cells by activating phospholipase C through B2 receptor and AT(1) receptor, respectively, and that endothelin-1 and PACAP also increase [Ca2+](i) in some folliculo-stellate cells.