Abstract
Bronchiolar ciliary cells were isolated from rat lungs. The β2-adrenergic regulation of ciliary beat frequency (CBF) was studied using video-optical microscopy. Terbutaline (an β2-agonist) increased CBF, and it also decreased the volume of the ciliary cells. These terbutaline actions were mediated by cAMP. Amiloride (1 μM) and bumetanide (20 μM) potentiated cell shrinkage and the CBF increase, and they shifted the terbutaline dose-response curve to the lower-concentration side. Quinidine (500 μM), in contrast, increased cell volume and suppressed the CBF increase. Moreover, a KCl solution containing amiloride (1 μM) and strophanthidin (100 μM) increased cell volume and suppressed the CBF increase, and then the subsequent removal of either amiloride or strophanthidin decreased cell volume and further increased CBF. NPPB (10 μM) or glybenclamide (200 μM) had no effects on the terbutaline actions. Thus, in terbutaline-stimulated ciliary cells, cell shrinkage enhances the CBF increase, in contrast, cell swelling suppresses it. However, hypo-osmotic cell swelling enhanced the CBF increase, while isosmotic swelling suppressed it. These suggest that isosmotic and non-isosmotic volume changes of terbutaline-stimulated bronchiolar ciliary cells may trigger different signaling pathways. In conclusion, terbutaline increases CBF and decreases the volume of the rat bronchiolar ciliary cells via cAMP accumulation under an isosmotic condition, and the isosmotic cell shrinkage enhances the CBF increase by increasing cAMP sensitivity. [Jpn J Physiol 54 Suppl:S76 (2004)]
