Characterization of bradykinin-induced endothelium-independent contraction in equine basilar artery.

This research investigates the impact of bradykinin, a peptide that promotes inflammation, on horse basilar artery rings with or without an endothelium, a thin layer of cells lining blood vessels. The researchers found that the presence of bradykinin lead to the contraction of these arterial rings regardless of the presence of endothelial cells, and the contractions were not mediated through known B1 and B2 receptors.

Study Design and Methods

• The researchers explored the effect of bradykinin (BK) on isolated horse basilar arterial rings.
• They conducted tests with and without the presence of endothelium, the tissue lining blood vessels.
• They examined the response of arterial rings under resting conditions and under a pre-contracted scenario through the use of prostaglandin F(2alpha).
• The impact and response of different receptor antagonists, inhibitors, and blocking drugs were analyzed in the presence of bradykinin.

Results

• Bradykinin led to a concentration-based contraction of the arterial rings.
• When the arterial rings were precontracted, there was no subsequent relaxation induced by bradykinin.
• The reaction to bradykinin was not altered by various B1- and B2-receptor antagonists like des-Arg(9)-[Leu(8)]-BK, HOE140, or NPC567.
• In a few instances, NPC567 led to concentration-based arterial ring contraction.
• Various inhibitors, blockers, and the process of endothelial denudation did not have an impact on the contraction instigated by bradykinin.
• Interestingly, nitric oxide synthase inhibitor (L-NNA) and cyclooxygenase inhibitor (indomethacin) led to contraction and relaxation of vessels respectively when under natural vascular tones.

Conclusions

• The study concluded that endothelial cells do not play a role in the contraction of equine basilar artery instigated by bradykinin.
• The arterial ring contraction induced by bradykinin was not mediated through the activation of known B1 or B2 receptors.
• Arachidonic acid by-products or neurotransmitters such as norepinephrine and nitric oxide were not believed to have a role in the bradykinin-induced contraction of the equine basilar artery.