Mechanism of Action
Kinin Receptor Activation
Kallidin activates both B2 receptors (constitutively expressed, high affinity) and B1 receptors (inducible, lower affinity for kallidin than des-Arg9-kallidin). B2 receptor activation through Gq coupling induces phospholipase C, IP3-mediated calcium release, and prostaglandin/nitric oxide synthesis, causing vasodilation, increased vascular permeability, and pain sensitization of sensory neurons.
Conversion to Bradykinin
Tissue aminopeptidase N converts kallidin to bradykinin by removing the N-terminal lysine. This conversion extends the overall kinin signaling duration at sites of tissue injury. Kallidin and bradykinin therefore act in sequence at inflammatory sites, with kallidin as the initial tissue product and bradykinin as the subsequent active metabolite.
Research Summary
Cardiovascular and Renal Protective Effects
PreclinicalTissue kallikrein-kinin system activity, including kallidin generation, has cardioprotective and renoprotective effects through B2-mediated vasodilation, anti-fibrotic signaling, and stimulation of NO synthesis. ACE inhibitors elevate kinin levels (including kallidin) partly explaining their cardioprotective benefit beyond blood pressure reduction.
ACE Inhibitor Mechanism
ClinicalACE (angiotensin-converting enzyme) degrades both bradykinin and kallidin. ACE inhibitors raise kinin levels as a secondary mechanism contributing to vasodilation, cardioprotection, and the dry cough side effect characteristic of this drug class. The kinin-elevating mechanism partially explains ACE inhibitor superiority over ARBs in certain outcomes.
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Research Protocols
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Kinin receptor pharmacology | 1-1000 nM | Single | Organ bath / cell assay |
| Pain sensitization model | 1-10 nmol intradermal | Single | Intradermal injection |
Endogenous peptide; no direct therapeutic use. Kinin receptor antagonists (icatibant) are therapeutic.
Interactions
Safety Profile
Kallidin is an endogenous inflammatory peptide with a short plasma half-life. Pathologically elevated kinins contribute to angioedema (hereditary angioedema involves bradykinin accumulation). Systemic kallidin administration would produce hypotension and pain sensitization. No therapeutic kallidin product exists.
References
- [1]Bhoola KD et al. (1992). Bioregulation of kinins: kallikreins, kininogens, and kininases. Pharmacological Reviews, 44(1), 1-80.
- [2]Regoli D and Barabe J (1980). Pharmacology of bradykinin and related kinins. Pharmacological Reviews, 32(1), 1-46.