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Summary
Histamine release does not cause bradykinin (BK)-induced leakage, but the H1 antagonist cetirizine unexpectedly inhibits BK reactions in skin and airways. Further research is needed to explain this effect, as cetirizine does not bind to the B2 receptor.
Area of Science:
- Pharmacology
- Immunology
Context:
- Histamine release was previously thought to mediate bradykinin (BK)-induced vascular leakage.
- Traditional H1-antihistamines did not inhibit BK-induced reactions in vitro and in vivo models.
Purpose:
- To investigate the mechanism of BK-induced reactions and the effect of cetirizine.
- To explore potential mediators beyond histamine in BK-induced responses.
Summary:
- Despite previous findings, cetirizine significantly inhibited BK-induced skin reactions and guinea pig bronchospasm.
- This inhibition was comparable to a specific BK antagonist (HOE 140).
- Cetirizine did not bind to the human recombinant B2 receptor in vitro, suggesting a novel mechanism of action.
Impact:
- Challenges the established understanding of BK-induced reactions.
- Suggests cetirizine may act through pathways independent of direct H1 receptor antagonism or B2 receptor binding.
- Opens new avenues for understanding and potentially treating BK-mediated inflammatory conditions.