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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.

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B3259 Bradykinin acetate salt powder, ≥98% (HPLC) 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.
B6769 des-Arg9-[Leu8]-Bradykinin acetate salt ≥97% (HPLC) Bradykinin receptor antagonist.
B1542 [Lys-des-Arg9]-Bradykinin ≥95% (HPLC) [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).
B6929 Lys-(des-Arg9, Leu8)-Bradykinin trifluoroacetate salt ≥95% B1 bradykinin receptor antagonist.
B5181 7-Methoxycoumarin-4-acetyl [Ala7-(2,4-Dinitrophenyl)Lys9]-Bradykinin trifluoroacetate salt >94% (HPLC)  
M0421 Met-Lys-[Ser2, Arg3, Pro5, Arg8]-Bradykinin ≥97% (HPLC) 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).
B1401 Bradykinin Fragment 1-5 ≥97% (HPLC) 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.
B1651 Bradykinin Fragment 1-7 ≥97% (HPLC)  
B1901 Bradykinin Fragment 2-9 ≥97% (HPLC) The des-arginine-1 bradykinin (BK) peptide (2-9) has no detectable contractile activity, inhibits ACE (angiotensin converting enzyme) and potentiates BK.
B1680 Bradyzide di(trifluoroacetate) salt hydrate ≥98% Potent, orally active, non-peptide B2 bradykinin receptor antagonist.
H157 HOE 140 ≥94% B2 bradykinin receptors are present in the sensory neurons. Activation of B2 receptor by bradykinin is associated with pro-inflammatory, pain producing and cardiovascular responses. HOE-140 is a selective B2 bradykinin receptor antagonist. Presence of HOE-140 suppresses the effects of bradykinin and has been shown to have anti-hyperalgesic response, particularly towards inflammatory pain.
K3628 Kininogen, low molecular weight from human plasma ≥95% (SDS-PAGE), lyophilized powder LMW kininogen is a major extracellular cysteine proteinase inhibitor. Tissue kallikrein releases bradykinin, a potent bronchoconstrictor and vasoactive agent, from both HMW and LMY kininogen.