Rapid and non-genomic reduction of intracellular [Ca2+] induced by aldosterone in human bronchial epithelium

1. Using a Ca2+ imaging system and fura-2 AM (5 mum) we showed that exposur e of polarised monolayers of human bronchial epithelial cells (16HBE14o- ce ll line) to aldosterone produced a fast intracellular [Ca2+] ([Ca2+](i)) de crease, in 70% of cells. Exposure to aldosterone (I nM) reduced the [Ca2+]( i) by 39 +/- 9 nM (n = 282, P < 0.0001) within 10 min, from a basal [Ca2+]( i) of 131 +/- 19 nm (n = 282). 2. The effect of aldosterone on [Ca2+](i) was not affected by inhibitors of the classical genomic pathway, cycloheximide (1 muM) or spironolactone (10 muM). The aldosterone-induced [Ca2+](i) decrease was inhibited by thapsiga rgin (1 muM), pertussis toxin (24 h at 200 ng ml(-1)), the adenylate cyclas e inhibitors 2,3'-dideoxyadenosine (200 muM)and MDL-12,330A hydrochloride ( 500 muM), and the protein kinase A inhibitor R-p-adennsine 3',5'-cyclic mon ophosphorothioate (200 muM). In addition, treatment of 16HBEI4o-monolayers with aldosterone (1 nm) inhibited by similar to 30% the large and transient [Ca+](i) increase induced by apical exposure to uridine triphosphate (UTP, 0.1 mM), a known secretagogue in airway epithelia. 3. Our results demonstrate for the first time that in human bronchial epith elial cells, aldosterone decreases [Ca2+](i) levels via a non-genomic mecha nism. The hormone-induced changes to [Ca2+](i) involve stimulation of thaps igargin-sensitive Ca2+-ATPase. via G-protein-, adenylate cyclase and protei n kinase A-coupled signalling pathways.