Substance P is generated in vivo following nasal challenge of allergic individuals with bradykinin.

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 of locally applied bradykinin on substance P generation was studied in nine individuals, allergic to grass pollen and six non-allergic controls. In the allergics 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 significant 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 short-term 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.