Ca²⁺ influx in the endothelial cells is required for the bradykinin‐induced endothelium‐dependent contraction in the porcine interlobar renal artery

Abstract

To determine the mechanism of bradykinin‐induced production of endothelium‐derived contracting factors, we monitored the changes in cytosolic Ca2+ concentration ([Ca2+]i) in in situ endothelial cells in porcine aortic valvular strips and the changes in [Ca2+]i of smooth muscle cells and force in porcine interlobar renal arterial strips using front‐surface fluorometry of fura‐2. In the presence of Nω‐nitro‐l‐arginine methyl ester, bradykinin caused an endothelium‐dependent transient elevation of [Ca2+]i and contraction in smooth muscle in the interlobar renal artery. This contraction was completely inhibited by a prostaglandin H2/thromboxane A2 receptor antagonist. In the absence of extracellular Ca2+, bradykinin failed to induce contraction. However, replenishing extracellular Ca2+ to 0.75 mm and higher induced an instantaneous contraction. However, replenishing Ca2+per se did not induce any contraction in the absence of bradykinin. Pretreatment with either 10−5m 1‐(β‐(3‐(4‐methoxyphenyl)propoxy)‐4‐methoxyphenethyl)‐1H‐imidazole hydrochloride (SKF96365) or 0.2 mm Ni2+ abolished the contraction induced by bradykinin in the presence of extracellular Ca2+. Treatment with 10−5m indomethacin completely inhibited the contractile response induced by Ca2+ replenishment, regardless of the timing of its application, before or after the application of bradykinin. In endothelial cells in the valvular strips, bradykinin caused a transient [Ca2+]i elevation in the presence of 1.25 mm extracellular Ca2+, but [Ca2+]i returned to the resting level within 10 min. Neither 10−5m SKF96365 nor 0.2 mm Ni2+ had any effect on the peak [Ca2+]i elevation, but decreased [Ca2+]i in the declining phase. In the absence of extracellular Ca2+, bradykinin induced a transient [Ca2+]i elevation to a level similar to that seen in the presence of 1.25 mm extracellular Ca2+. However, [Ca2+]i then rapidly returned to the prestimulation level within 5 min. Subsequent Ca2+ replenishment to 0.75 mm and higher in the presence of bradykinin elevated [Ca2+]i to significantly higher levels than the resting level seen in the media containing 1.25 mm Ca2+. In conclusion, Ca2+ influx in the endothelial cells is essential for bradykinin to induce endothelium‐dependent contraction in the porcine interlobar renal artery.

Flow enhances the agonist-induced responses of the bradykinin receptor (B2) because of its lectinic nature: Role of its oligosaccharide environment

“…In addition, the amplitude of the contractile responses of the vascular smooth muscle is a direct indicator of endothelial paracrine signaling [20][21][22][23][24][25]. This preparation constitutes a system more similar to an in vivo model, making it a suitable agile system for quantitative studies on the mechanisms of flow-activation of endothelial surface layer endothelial processes with changes in vascular smooth muscle contraction serving as an [20][21][22][23][24][25].…”

“…Intravascular bradykinin acts exclusively and selectively by activation of bradykinin B2 receptors in the endothelial surface layer [36]. Although bradykinin-induced vasodilation is frequently reported, in the guinea pig carotid artery as well other blood vessels, the response is a receptor-mediated constriction [19][20][21][22][23][24][25]. This vasoconstriction response was blocked by Hoe 140, a specific bradykinin B2 receptor antagonist (not shown) [37].…”

“…Bradykinin is an agonist capable of causing vasodilation, vasoconstriction or both, and, although vasodilation is commonly reported, vasoconstriction occurs in various vascular preparations [19][20][21][22][23][24][25]45]. To illustrate the vasoconstriction response at different concentrations of bradykinin, original recordings are shown in figure 1.…”

“…An isolated blood vessel preparation was selected because it is a simple anatomical model and frequently used to study functional interactions between endothelial and adjacent smooth muscle cells [16][17][18][19][20][21][22][23][24][25]. For our study we chose the isolated guinea pig carotid artery which has an internal diameter of about 0.5 mm, a length of 1.5 ± 0.5 cm and can be perfused at a controlled flow.…”

“…L-NAME (L-N 6 -nitroarginine methyl ester), an analog of arginine that inhibits nitric oxide production, is expected to potentiate the bradykinin concentration-constrictor response curves because the dilation is prevented [19][20][21][22][23][24][25]35]. As described for group 1, control dose-response curves to bradykinin were obtained at 11 and16 ml/min.…”