Pharmacological profiles of the human and rabbit B1 receptors

Twenty-two peptides related to kinins were used (i) to examine some chemical features required for the human and rabbit B1 receptor activation or blockade and (ii) to establish the existence of a correlation between the pharmacological spectrum of the B1 receptor obtained on the rabbit aorta (rbA) and the human umbilical vein (hUV). The apparent affinities of these peptides were measured in vitro using classical bioassays and are expressed in terms of pD2 (for agonists) or pA2 values (for antagonists). Selectivity for the B1 receptor was demonstrated by testing the peptides against the effect of bradykinin (BK) on the hUV and the rabbit jugular vein (rbJV), two preparations containing B2 receptor-mediating vasoconstriction. The results show that (i) lysyl-peptide agonists and antagonists demonstrate higher affinities than nonlysyl compounds on human and rabbit B1 receptors, (ii) peptides containing hydrophobic D-residues (e.g., Tic, beta Nal, Hyp(trans-propyl), Igl) in position 7 are suitable for B1 receptor antagonism, and (iii) the additive substitution of an Oic residue in position 8 leads to nonselective kinin receptor antagonists. Moreover, a high (r = 0.92) and positive (regression slope = 0.99 +/- 0.09) correlation between the affinities measured for the kinin analogues in two B1 receptor bioassay systems has been revealed. Based on the similarity of pharmacological profiles observed in the rabbit and human B1 receptors, we suggest that the B1 receptor domain in which peptide agonists and antagonists interact may be similar in these two species.