ANGIOTENSIN-II STIMULATES AIRWAY CILIARY MOTILITY IN RABBIT CULTURED TRACHEAL EPITHELIUM

We studied the effect of angiotensin II on ciliary activity in cultured rabbit tracheal epithelium in vitro. Administration of angiotensin II (10-6 M) elicited an increase in ciliary beat frequency (CBF), as assessed by a photoelectric method, from the baseline value of 906±21 to 1260±33 beats min-1 (mean±SE, P<0.001). This ciliostimulatory effect was dose-dependent, with the maximal increase and EC50 value being 35.6±5.2% (P<0.001) and 5x10-12 M respectively. Nifedipine, Ca2+-free medium, indomethacin and the phospholipase A2 inhibitor mepacrine, but not nordihydroguaiaretic acid, reduced the change in CBF. The ciliostimulation induced by angiotensin II was abolished by pretreatment of tissues with [Sar1-Ile8]angiotensin II, an angiotensin II receptor antagonist. Angiotensin II did not increase cyclic AMP levels in epithelial cells. These results suggest that angiotensin II interacts with its specific receptors and stimulates airway ciliary activity through a Ca2+-dependent prostaglandin release, without affecting intracellular cyclic AMP levels. Thus, angiotensin II may modulate mucociliary transport function in the respiratory tract.