Receptors for bradykinin and kallidin

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Abstract
To establish if bradykinin (BK) and Lys-bradykinin (Lys-BK), alias kallidin, act on the same or on different receptors, experiments were performed on strips of cat terminal ileum and of rabbit aorta. The 1st preparation contained receptor B2 and the 2nd had the newly identified receptor B1. The criterion used for establishing the identity of receptors for BK and Lys-BK in the cat ileum (receptor B2) was desensitization, while for the rabbit aorta (receptor B1) apparent affinity (pA2 value) was measured of a competitive and specific inhibitor of BK, [Leu-OMe8,des-Arg9]-BK. Since cat ileum desensitized with BK or Lys-BK showed a significant decrease or a complete disappearance of the response to the other agent, while maintaining full sensitivity for histamine, and since the pA2 values of [Leu-OMe8,des-Arg9]-BK against BK and Lys-BK were identical in the rabbit aorta, the 2 kinins acted on the same types of receptors.