Bradykinin is a vasoactive peptide, nine amino acids in length, cleaved from high-molecular-weight or low-molecular-weight kininogen by tissue or plasma kallikrein. Originally discovered by Rocha e Silva while investigating shock caused by snake venom, bradykinin lowers blood pressure by vasodilation. Because angiotensin converting enzyme (ACE) proteolytically inactivates bradykinin, ACE inhibitors potentiate the action of bradykinin. Other bradykinin activities include natriuresis, diuresis, smooth muscle contraction, and involvement in pain. This multifunctional peptide binds to two genetically distinct G-protein coupled receptors. The B2 bradykinin receptor is constitutive in many tissues, while the B1 receptor is induced in injured and inflamed tissue. Preferred agonists for the B1 receptor lack the amino-terminal arg.
Sigma offers a variety of agonists and antagonists for both receptors. Most are peptides with modifications or substitutions. Laboratory researchers may also find bradyzide, a non-peptide B2 antagonist, useful because it is selective for the rodent receptor.
Bradykinin is a pro-inflammatory peptide that acts through G-protein-coupled receptors. It activates sphingolipid metabolism. Fibroblasts treated with bradykinin produce a rapid and important increase in ceramide which is followed by a transient rise in sphingosine content. The peptide also increases ceramide cellular content by rapidly mobilizing neutral glycolipids. Bradykinin plays an important role in the regulation of fluid and electrolyte balance, smooth muscle contraction, vasodilation and capillary permeability. The bradykinin potentiators, which possess no bradykinin activity themselves, enhance the activity of bradykinin.
[Des-Arg10]-kallidin is a bradykinin B1 receptor agonist. It strongly upregulates the B1 receptor and is blocked by a specific protein kinase C inhibitor. The upregulation is correlated with the induction of transcription factor nuclear factor κB (NF-κB).
Met-Lys-[Ser2, Arg3, Pro5, Arg8]-Bradykinin (MKRSRGPSPRR) is a neuropeptide found in Aplysia californica with high sequence homology to bradykinin and kallidin. It may be used as a substrate to study the specificity and kinetics of angiotensin-converting enzyme(s) (ANCE).
The bradykinin (BK) fragment (1-5) (RPPGF) is among the most stable of naturally occurring metabolites. It may be used as a marker for BK production in vivo. It is known that an intact Arg residue in the C-terminus is required for biological activities. BK 1-5 is the minimal peptide that inhibited α-thrombin-induced platelet aggregation and secretion and calcium mobilization. It also prevented α-thrombin from cleaving the thrombin receptor peptide, NATLDPRSFLLR, between arginine and serine. Such antithrombin activities of BK 1-5 may contribute to the cardioprotective nature of kinins.