Tetracaine, propranolol and trifluoperazine inhibit thyrotropin releasing hormone-induced prolactin secretion from GH3 cells by displacing membrane calcium: further evidence that TRH acts to mobilize cellular calcium.
TRH stimulation of prolactin release from GH3 cells is associated with loss of cellular Ca2+. Chlortetracycline (CTC), a fluorescent probe of Ca2+ in biological membranes, was previously employed to monitor indirectly changes in membrane Ca2+ in GH3 cells. Tetracaine, propranolol and trifluoperazine, agents that are known to displace Ca2+ from biological membranes, were utilized to demonstrate more rigorously that TRH affects cellular membrane Ca2+ in GH3 cells. Tetracaine (1 mM), propranolol (1 mM), and trifluoperazine (0.03 mM) inhibited basal and TRH-stimulated prolactin release, decreased cellular 45Ca2+ content and decreased cell-associated CTC fluorescence. Most importantly, these agents abolished the decrease in CTC fluorescence induced by TRH. These data suggest that tetracaine, propranolol and trifluoperazine displace membrane Ca2+ in intact GH3 cells and offer further evidence that TRH acts to mobilize cellular Ca2+ from a membrane-bound pool(s) during stimulation of GH3 cells.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D013748:Tetracaine / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000037:antagonists & inhibitors*; D014268:Trifluoperazine / Q000494:pharmacology
D013748:Tetracaine; D014268:Trifluoperazine; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D011433:Propranolol; D002118:Calcium