Background Bradykinin, a potent inflammatory mediator, is released during allergic and non-allergic rhinitis and asthma in man. Nasal bradykinin challenge induces a dose-dependent plasma leakage into the nasal cavity and relevant symptoms of rhinitis.
Objective We now report on substance P generation during nasal bradykinin challenge in vivo.
Methods The effect ot locally applied bradykinin on substance P generation was studied in nine individuals, allergic to grass pollen and six non-allergic controls. In the allergies TAME-esterase activity, histamine and substance P concentrations were measured in nasal lavages and correlated to the clinical symptoms.
Results Substance P concentrations in nasal lavages increased in a dose-dependent fashion during nasal bradykinin challenge in both groups. In the allergic group Substance P-increases correlated with the production of TAME-esterase activity (r= 0.9. P < 0.05) whereas these allergic individuals did not produce any histamine increases. The generation of substance P and the increase of TAME-esterase activity was associated with the onset of clinical symptoms. Correlation of oedema and hypersecretion to substance P were signiticant by linear regression analysis (r = 0.88, P < 0.005 and r= 0.89. P < 0.02, respectively). Bradykinin induced irritations like burning and itching were shortterm and rare. Serial dilutions of nasal washes produced Substance P-RIA displacement curves that paralleled the standard curve and recovery of standard substance P that was added to nasal washes was 76 ± 4% (mean ± sem), n= 8.
Conclusion Bradykinin induces in vivo a dose-dependent plasma leakage into the nasal cavity without affecting mast cells, but stimulates nerve endings resulting in the release of the neuropeptide substance P.
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