Histamine release from rat peritoneal mast cells by kinin antagonists

Kinins are known to be potent releasers of histamine. In the present study, the B2 antagonist analogues of bradykinin (BK) and kallidin (KD): [( Thi6,9,D-Phe8]KD, [Thi5,8,D-Phe7]BK) were also found to be potent releasers of histamine from rat mast cells and not to exert any antagonistic effect. Similarly, two B1 receptor antagonists, des-Arg10-[Leu9]KD and des-Arg9-[Leu8]BK, were shown to promote histamine release and acted only as agonists. The order of potency of these analogues was the following: [Thi6,9,D-Phe8]KD greater than [Thi5,8,D-Phe7]BK greater than des-Arg10- [Leu9]KD greater than des-Arg9-[Leu8]BK. The high activity of some of these compounds suggests that (1) the potency of kinins for histamine release from rat mast cells not only increases in parallel with the number of positively charged amino acids (Lys, Arg) but also, because of others factors such as peptide conformation, receptor binding affinity or receptor accessibility, (2) the histamine release by kinins is either a non-specific effect not mediated by receptors or, if receptors are involved, these sites may be different from other kinin receptors (i.e. B1 or B2).