Angiotensin I-converting enzyme (kininase II; ACE) inhibitors, antibodies to ACE and slowly cleaved substrates of ACE potentiate the effect of bradykinin and its analogs on their B2 receptors independently of blocking peptide metabolism. ACE inhibitors also resensitized the receptors desensitized by the ligand (tachyphylaxis). The studies were performed on isolated organs and cells co-transfected with the receptor and the enzyme or constitutively expressing them. This enhancement of the effect of B2 ligands is attributed to a crosstalk between the enzyme and the receptor, and not to a direct action on the receptors. It might reflect some of the local activities of ACE inhibitors.