Nitric oxide is a regulator of mucociliary activity in the upper respiratory tract

The in vitro effects of the nitric oxide (NO) substrate L-arginine on ciliary beat frequency and the in vivo effects of the NO donor sodium nitroprusside (SNP) on mucociliary activity were investigated in the rabbit maxillary sinus mucosa with photoelectric techniques. L-Arginine increased ciliary beat frequency in vitro with a maximum response of 27.1% ± 6.4% at 10-3mol/L, and this effect was reversibly blocked by pretreatment with the NO synthase (NOS) inhibitor NG-nitro-L-arginine, whereas D-arginine had no such effect. SNP increased mucociliary activity in vivo, the peak response of 36.8% ± 4.2% being obtained at the dose of 30.0 μg/kg. No tachyphylaxis was observed after repeat challenge with SNP. The increase in mucociliary activity caused by SNP was largely unaffected by pretreatment with the calcium channel blocker nifedipine, the cyclooxygenase inhibitor diclofenac, and the cholinergic antagonist atropine. The nonselective β-blocker propranolol delayed the peak response of SNP to 7 to 8 minutes a...